Servo Blog

September in Servo: who knows?

2026-10-26T00:00:00Z

Servo 0.7.0 contains all of the changes we landed in August, which came out to a new record of 566 commits!

The developer tools console now eagerly evaluates JS inputs, allowing faster feedback (@freyacodes, #47527).

We’ve shipped new web platform features:

the :checked pseudoclass (@skyz1, #47987)
the user-select property (@SimonSapin, @mrobinson, #48137)
the element (@rayguo17, #46974)
CSS typed arithmetic (@Loirooriol, #48338)
the alpha() CSS function (@Loirooriol, #48344)

Plus a bunch of new DOM APIs:

parentRule on CSSRule and CSSStyleDeclaration (@skyz1, #47743)
version on HTMLHtmlElement (@SilvioPilato, #47786)
getComposedRanges() and direction on Selection (@mrobinson, #47683)
baseURL on CSSStyleSheet (@Gae24, #47783)
CSS modules(@Gae24, #47813) and text modules (@Gae24, #47863)
getContextAttributes() on CanvasRenderingContext2D and OffscreenCanvasRenderingContext2D (@Taym95, #47868)
the Content-Language header (@TimvdLippe, #47930)
dir on Document (@yezhizhen, #48170)
SVGAElement, SVGPatternElement, SVGTSpanElement, SVGTextContentElement, SVGTextElement, SVGTextPositioningElement (@mu-mostafa98, #48174)
the MLKEM768-X25519 algorithm for WebCrypto (@kkoyung, #48240, #48282, #48313, #48350)
roundRect() on CanvasRenderingContext2D (@yezhizhen, #48293)
paintTime and presentationTime on PerformancePaintTiming (@shubhamg13, #47926)
getCueAsHTML() on VTTCue (@TimvdLippe, #48146)

Security

We upgraded to SpiderMonkey v153.3 and mozangle v0.7, both of which included fixes for security bugs reported upstream (@sagudev, #48176, #47655, #48259).

Real world compat

The egui.rs demo now works as expected with --pref dom._webegpu_enabled.

This Candy Crush game.

We’re interested to hear how well your favourite websites run in Servo! Report successes in this Zulip thread or this Github discussion, and failures in our GitHub issues.

Work in progress

Our accessibility tree (--pref accessibility_enabled) now reports geometry bounds for inline elements (@alice, #47905) and does much less work when responding to DOM changes (@alice, @mrobinson, #47690). Additionally, elements with display: none are reported as hidden (@alice, #47772).

We had lots of conformance improvements for our WebGL2 implementation (--pref dom_webgl2_enabled) (@mxmgorin, #48423, #48441, #48470, #48479, #48495, #48473, #48536).

Support for WSIWYG editors (which rely heavily on contenteditable) is going very well: keyboard inputs are now hooked up when --pref dom_exec_command_enabled is present, so many editors are now usable (example).

Closed captioning for video elements is making progress. Text tracks now fire enter, exit, and cuechange events (@TimvdLippe, #47725). Media elements now return the full sorted list of text tracks (@TimvdLippe, #47785). Adding cues to a text track now sets that track correctly (@TimvdLippe, #48012). Text track objects now reflect the attributes of the associated <track> element. Text track URLs are now fetched at the correct time (@TimvdLippe, #48325), and active cues are computed correctly (@TimvdLippe, #48305), while text track cues are ordered as expected (@TimvdLippe, #48368). Additionally, WebVTT parsing can now recover from errors (@TimvdLippe, #48391).

The Sanitizer API (--pref dom_sanitizer_enabled) now accepts the javascriptURLs property (@skyz1, #47867).

IndexedDB continues to improve: tables no longer error if unrelated tables contain duplicate index names (--pref dom_indexeddb_enabled) (@leowatts, #47936). Additionally, we implemented openCursor() and openKeyCursor() on IDBIndex (@kuntal-devrat, #48281), as well as advance(), continue(), and continuePrimaryKey() on IDBCursor (@kuntal-devrat, #48400).

We implemented the getTimeline() and setTimeline() methods for the Animation interface (--pref dom_web_animations_enabled) (@simonwuelker, #48122).

Embedding API

There’s a new API for integrating with accessibility tools: Servo::forward_accessibility_action (@alice, @mrobinson, #48512).

There is also an API to clear session history: WebView::clear_session_history (@Narfinger, #47483).

The WebView::set_throttled API has been removed (@mrobinson, #39923). Throttling automatically occurs when a WebView is hidden and stopped when shown.

The WebViewDelegate::notify_focus_changed method was removed, along with the Servo methods focus and blur (@mrobinson, #48364). Embedders must call WebView::set_focused whenever a WebView has gained or lost system focus.

The webgl feature has been added to the default_web_features feature (@janeoa, #47866). If an embedding does not want to ship with WebGL support they will now need to disable default features.

Multiprocess mode is enabled at build time with the new Cargo feature multprocess (@Narfinger, #47360). To remove support for this feature (reducing binary size by ~2MB), build Servo with default features disabled.

Two new preferences exist to tune garbage collector behaviour: js_mem_gc_malloc_threshold_base_mb and js_mem_gc_urgent_threshold_mb (@mxmgorin, #47999). These can help on memory-constrained devices, and more information is available in the SpiderMonkey source (base, urgent).

For users and developers

It is now possible to cross-compile the OpenHarmony build from Windows hosts (@jschwe, #48392).

Unhandled promise rejections are reported to the JS console (@TTyChud, #48486), making it easier to narrow down web compatibility issues in Servo.

The OpenHarmony SDK was updated to API level 23 (@Narfinger, #48505).

Pressing Control+A (or Command+A on macOS) now selects all the content in a document (@dzfrias, @mrobinson, #48025).

Embedder-originating JS (e.g. devtools console or embedding APIs) will always execute, even in documents that disable scripting via sandboxing or CSP (@derdilla, #48394).

Performance and stability

We improved performance by removing unnecessary allocations (@Narfinger, @TimvdLippe, @yezhizhen, #47689, #47839, #47838, #47982, #48006, #48036, #48099, #48204, #48127, #48218, #48357, #48386, #48422, #48440, #48452, #48508), preallocating more when building vectors (@jschwe, @Narfinger, @sagudev, @webbeef, #47455, #47613, #48026, #48398), and avoiding IPC in single process mode (@leowatts, @Narfinger, @Uiniel, @TTyChud, #47691, #47718, #48002, #48073, #48476, #48435).

We also sped up Servo by reducing interactions with the GC (@TimvdLippe, @Narfinger, #47818, #48257, #48396) and doing less work when modifying selections (@SimonSapin, #47579), dispatching events (@webbeef, #48078), calculating font metrics (@RichardTjokroutomo, #48238), and indexing window frames (@mrobinson, #47832).

We reduced memory usage in common cases by reusing buffers (@Narfinger, #47751), clearing more page-specific data (@Radeonares32, @Narfinger, @jschwe, @mrobinson, @mxmgorin, #47651, #47806, #47805, #48166, #48295, #48297, #48016), compacting data structures (@Narfinger, @webbeef, @SimonSapin, @mrobinson, #47776, #48039, #48050, #47742, #48301, #48296, #48105), and sharing more buffers (@jdm, #47998).

We turned on thread affinity boosting on Linux, which can improve performance on some CPU architectures (@jschwe, #47058).

We’re working on statically preventing a footgun that can lead to uncollectible GC cycles and leaking memory (@Gae24, @jdm, @lumiscosity, @SilvioPilato, @sahilnyk, @TTyChud, @kuntal-devrat, @MohamedAli00949, #47941, #48013, #48021, #48035, #48033, #48051, #48072, #48171, #48209, #48248, #48246, #48264, #48285, #48311, #48408, #48053, #48156, #48186, #48223, #48315, #47872, #47698, #47682, #47735, #47816, #47817, #47794, #47909, #47934, #47935, #47954, #48022, #47955, #48058, #48228, #48247, #48261, #48280, #48302, #48316, #48328, #48346, #48355, #48262, #48377, #48304, #48378, #48388, #48432).

More on the web platform

CSS images now delay the load event, leading to more consistent behaviour for engine users performing visual rendering (@TimvdLippe, #48199).

Interactive selections in documents continued to improve. They now can span shadow trees (@mrobinson, @SimonSapin, #47931), and have consistent heights and positions (@mrobinson, #47937), plus there are new context menu entries to copy and select all (@mrobinson, #48101). Additionally, image-based content shows when it is part of a selection (@mrobinson, #48149).

There are more useful error messages for methods on Document (@eachra-bawn, #47835).

We also fixed bugs related to visibilityState on Document (@yezhizhen, #47908), containsNode() on Selection (@mrobinson, #47938), setKeyframes on KeyframeEffect (@simonwuelker, #48103), selections when focusing a text input (@mrobinson, #48107), AudioParam clamping and automation (@kevlu93, #48351, #48347), PannerNode outputs (@kevlu93, #48510), the muted attribute on HTMLMediaElement (@TimvdLippe, #48403), placeholders in text inputs (@jdm, #47761), animations when modifying document stylesheets (@SharanRP, #48000), gradient color stops (@BudiArb, #48288), sticky table rows (@TTyChud, #48380), ::first-letter (@Loirooriol, #48307), text-wrap-mode (@mrobinson, #48469), OTF fonts (@wood-ghost, #47904), CSS and nosniff (@sahvx655-wq, #45481), Sec-Fetch- headers and redirects (@TimvdLippe, #48203)

New contributors

A special thanks to the following people for landing their first patch in Servo:

Interested in helping build a web browser? Take a look at our curated list of issues that are good for new contributors!

Donations

Thanks again for your generous support! We are now receiving 8144 USD/month (+1% from August) in recurring donations. This helps us cover the cost of our speedy CI and benchmarking servers, one of our latest Outreachy interns, and funding maintainer work that helps more people contribute to Servo.

Servo is also on thanks.dev, and already 37 GitHub users (+1 from August) that depend on Servo are sponsoring us there. If you use Servo libraries like url, html5ever, selectors, or cssparser, signing up for thanks.dev could be a good way for you (or your employer) to give back to the community.

We now have sponsorship tiers that allow you or your organisation to donate to the Servo project with public acknowlegement of your support. If you’re interested in this kind of sponsorship, please contact us at join@servo.org.

8128 USD/month

10000

Use of donations is decided transparently via the Technical Steering Committee’s public funding request process, and active proposals are tracked in servo/project#187. For more details, head to our Sponsorship page.

August in Servo: CSS Grid, text selection, and more!

2026-10-09T00:00:00Z

Servo 0.6.0 contains all of the changes we landed in August, which came out to 417 commits!

The big news is that we’ve turned on support for CSS Grid by default (@nicoburns, #45621). This has had a huge positive impact on the visual appearance of many websites!

We’ve shipped several new web platform features:

touch-action (@yezhizhen, #47043)
animation-composition (@nicoburns, #47405)
color-scheme (@TimvdLippe, #47042)
full-width, math-auto, full-size-kana values for text-transform (@SimonSapin, #47160, #47160, #47225)

Plus a bunch of new DOM APIs:

requestAnimationFrame() on DedicatedWorkerGlobalScope (@Taym95, #46232)
ancestorOrigins on Location (@TimvdLippe, @mrobinson, #46056)
imagesrcset and imagesizes on <link rel=preload as=image> (@lumiscosity, @TimvdLippe, #47103)
style on CSSFontFaceRule (@simonwuelker, #47388)
isReloadNavigation and isHistoryNavigation on Request (@Taym95, @yezhizhen, #46917)
name=color-scheme on <meta> (@TimvdLippe, @jdm, #46993)
focusin and focusout events (@RichardTjokroutomo, @yezhizhen, #46980)
new TextEvent() (@moamenhesham0, @mrobinson, #47391)
PeriodicWave and createPeriodicWave on BaseAudioContext (@kevlu93, #47492)

This release also contains significant improvements to navigation, document loading, and session history, which are some of the gnarliest parts of the HTML specification. Who knew that loading about:blank was so complicated? The upshot to all this work is that pages that open additional windows or include iframes work much more reliably.

This is another big update, so here’s an outline:

Security

We upgraded to SpiderMonkey v153, which brings many new security and crash fixes to Servo’s JavaScript engine integration (@sagudev, @Gae24, #47489).

Navigating away from a document that activated fullscreen mode now exits fullscreen mode (@shubhamg13, @jdm, #47123).

Real world compat

CSS Grid enabled by default means that many websites with traditional grid layouts now look correct, like rustweek.org.

v0.5.0

v0.6.0

2026.rustweek.org

It also makes a lot of websites look better that you wouldn’t assume rely on CSS Grid:

v0.5.0

v0.6.0

labs.jensimmons.com

Panning gestures initiated by touch inputs now lock to the dominant axis (@yezhizhen, #46983). This results in more predictable panning when interacting with pages in Servo.

We fixed a crash affecting gumroad.com.au (@lumiscosity, #47266).

We’re interested to hear how well your favourite websites run in Servo! Report successes in this Zulip thread or this Github discussion, and failures in our GitHub issues.

Work in progress

Accessibility support in Servo continues to make great strides; it can be enabled with the --pref accessibility_enabled command line argument. Servo now reports positions and sizes for items in the content accessibility tree (@philocalyst, @alice, @mrobinson, #46996), allowing macOS VoiceOver to work more reliably. We also report many ARIA roles for web content elements to accessibility toolkits (@mukilan, #47318).

Full list of supported roles

alert
banner
blockquote
caption
code
complementary
contentinfo
definition
deletion
directory
document
emphasis
feed
figure
generic
insertion
list
log
main
math
navigation
none
note
paragraph
presentation
rowgroup
search
status
strong
term
time
timer

Servo’s support for Document.execCommand() is rapidly improving, and can be enabled with --pref dom_exec_command_enabled. We fixed issues with the inserttext command (@Psychpsyo, #47224, #47306), editing uneditable content (@Psychpsyo, #47362), computing contained nodes (@TimvdLippe, #47429), adjusting selections in contenteditable (@mrobinson, #47393, #47581, #47581), and implemented the indent and insertLineBreak commands (@Psychpsyo, #47416, #47445).

We made a lot of progress on the LargestContentfulPaint performance metric, implemented behind the --pref largest_contentful_paint_enabled argument. Servo now supports the element and loadTime attributes, (@shubhamg13, #46553, #47475), URLs for video element posters (@shubhamg13, #43376), accurate size information (@shubhamg13, #43378), and painting text nodes (@shubhamg13, #47212).

There was preparatory work for a future AudioWorklet implementation (@niyabits, #46856, #47016, #47199). See Niya’s blog post about her Outreachy project for more details!

We’re continuing work on the ServiceWorker feature, which can be enabled with --pref dom_serviceworker_enabled. This month we implemented the CookieStore interface behind the --pref dom_cookiestore_enabled command line argument (@Taym95, #47044) as well as the Cache interface (@gterzian, #47220).

Servo now supports a disk-backed HTTP cache that can be enabled with --pref network_http_disk_cache (@Narfinger, #43819). This cache persists between runs, but there is not yet any way to clear it.

Embedding API

Breaking change: WebView::toggle_sampling_profiler has been removed (@lumiscosity, #47014). To perform sampling profiling on Servo, follow the instructions in the book.

Breaking change: The variants of MouseButton have been renamed to Primary, Secondary, and Auxiliary (@mrobinson, @SimonSapin, #47327).

We’ve added several new Cargo features reflecting common usage patterns:

default_web_features, to include optional web platform features in the build (e.g. WebXR and WebGPU) (@jschwe, #44032)
bundled, to include required resources in the binary (@jschwe, #44032)
brotli-compression-stream, enabling support for brotli content in the CompressionStream/DecompressionStream web APIs (@Narfinger, @jdm, #47197)
webcrypto, to enable support for the Crypto and WebCrypto web APIs (@Narfinger, #47198)
webgl, to enable support for WebGL (@janeoa, #47200)

For users and developers

One visible change is that interactive text selection now works! This is the result of lots of work across our script and layout code to ensure it respects the actual geometry of the page content (@mrobinson, @SimonSapin, #47022, #47025, #47329, #47358, #46982, #47425, #47438, #47437, #47581, #47070, #47048, #46963).

Building Servo now requires at least Clang 19 on all platforms (@jschwe, #47421). Additionally, the cargo-ohos tool is now required for building for OpenHarmony (@jschwe, #47334).

Debug builds on Windows can now complete successfully (@jschwe, #47372).

Linux arm64 builds have been customized to work on Raspberry Pi 5 (@mukilan, #47113). Any libservo embedders targeting the same platform will require a similar change if they are using jemalloc.

servoshell

Under Wayland and OpenHarmony, we now integrate with the system clipboard (@TheZoq2, @yezhizhen, @jschwe, #46938, #47177).

The macOS command key and Windows logo key is now reported as Meta instead of Super (@eachra-bawn, #47330).

The Android port has had many rough edges filed off as part of modernizing it for the Compose UI (@veyndan, #47656, #47491, #47494, #47697, #46955, #47644, #47652, #47276, #47277, #47299, #47439) and converting its implementation to Kotlin (@veyndan, #46926, #46925, #46951, #46965). Library consumers are no longer responsible for implementing pause and resume support (@veyndan, #47555).

Meanwhile, the OpenHarmony port now supports external keyboards with US keyboard layouts (@jschwe, #47359). Additionally, there are now better fallback font selections for CJK characters (@RichardTjokroutomo, #47116, #47664).

Setting the device_pixel_ratio_override preference is no longer ignored on Android and OpenHarmony (@jschwe, #47081).

Performance and stability

There were many small changes this month that removed unnecessary allocations (@Narfinger, @jschwe, @yezhizhen, #47264, #47147, #47066, #47249, #47249, #47285, #47307, #47343, #47361, #47395, #47427, #47454, #47474, #47506, #47479, #47530, #47541, #47566, #47509, #47622).

We also reduced GC interactions leading to better JS performance (@jdm, @Narfinger, @webbeef, @TimvdLippe, @mrobinson, #47513, #47250, #47158, #47165, #47049, #47251, #47510, #46981).

On platforms that memory map font data (such as OpenHarmony and macOS), we can now save time that would otherwise be spent loading font files from disk (@jschwe, #47029). Similarly, reading system fonts is no longer in the critical path of starting up the engine (@Narfinger, @jdm, #46476).

There were were also a number of savings in the final binary size (@jschwe, @kkoyung, @Narfinger, @jschwe, #47211, #47214, #47210, #46950).

We fixed crashes related to media playback (@calvaris, #46891), the 2d canvas renderer (@yezhizhen, #46915), fonts with negative line gaps (@jschwe, #47374), and resolving fonts variants (@simonwuelker, #47356).

Canvas renderer worker threads can now be adjusted by the thread_pool_canvas_workers preference, allowing more performance granularity according to embedder needs. (@jschwe, #46691, #47018)

We’ve continued our long-running effort to use the Rust type system to make Servo’s integration with SpiderMonkey safer and more reliable (@jdm, @treetmitterglad, @Narfinger, @Gae24, #47398, #47296, #47051, #47005, #47323, #47297, #47322, #47368, #47446, #47317). We’re also working on statically preventing a footgun that can lead to uncollectible GC cycles and leaking memory (@Gae24, #47355, #47650).

Historically, about:memory has reported all memory usage by Rust implementations of JS APIs as one undifferentiated js/malloc-heap number. We now break it down by memory usage of nodes in document trees (@pylbrecht, #46931) and interfaces that are not part of the DOM (@jdm, #47531). We also report memory usage for the network stack’s cookie database (@Narfinger, #47248) and the canvas renderer backend (@janeoa, @jdm, #46958).

We’ve added an experimental threadboost mechanism (@jschwe, @mrobinson, #46843, #47027) that has been observed to improve Speedometer results by 50% and allow canvas rendering to reach 60 FPS. This is initially enabled for OpenHarmony, but future expansion to other Linux-based platforms is expected.

More on the web platform

We upgraded to resvg 0.48, fixing many issues with SVG images with missing width/height attributes that specified a viewBox (@nicoburns, #46937).

Upgrading to Taffy 0.14 fixed a number of CSS grid-related crashes, support for grid names, better intrinsic sizing, and improved performance (@nicoburns, #47031, #47493). We also fixed some issues in the Taffy grid integration for more accurate baselines (@nicoburns, #47518).

Session history traversals (i.e. navigating backwards or forwards in history) now wait for any outstanding traversal to complete (@mrobinson, #47293, #47485). Meanwhile, navigations to about:blank are skipped if the initial about:blank document is present (@jdm, #47074).

about:blank documents no longer use the asynchronous HTML parser (@jdm, #47050), and no longer report a readyState of LOADING (@mrobinson, #47450). Opening auxiliary windows will wait to dispatch the load event until the initial about:blank document has been replaced (@jdm, @mrobinson, #47442, #46975).

For non-about:blank content, we also made the document loading phases more reliable (@TimvdLippe, @mrobinson, #47426), improved conformance of javascript: URL evaluation and navigation target selection (@mrobinson, #47486, #47516), and addressed longstanding compatibility issues with cross-origin Window and Location objects (@mrobinson, #47549).

Our media playback has improved; we fixed several issues around canPlayType() on HTMLMediaElement that allow Servo to report that MP4 content is playable (@jdm, #47612, #47641, #47670).

Input elements with the autofocus property inside of a <dialog> now receive focus when that dialog is opened (@skyz1, @mrobinson, #45826).

We improved the exception error text for numerous web APIs (@jdm, @eachra-bawn, #46960, #47124, #47168, #47580, #47430, #47127).

We also fixed issues related to many other APIs, including:

matching other browsers’ treatment of Access-Control-Allow-Headers (@yezhizhen, #47600)
WebCrypto CryptoKey usage checks (@kkoyung, #47112, #47141, #47178) and key lengths (@kkoyung, #47452, #47453)
determining referrers when navigating (@mrobinson, #47487)
reading name on Window inside of iframes (@TimvdLippe, @jdm, #47270)
many edge cases around determining dirty roots for incremental layout (@mrobinson, #46906)
edge cases around compareDocumentPosition on Node (@SimonSapin, #46886)
resolving ties in web font matching (@simonwuelker, #47449)
Range.getClientBoundingRect()/getClientRects() for empty ranges (@yezhizhen, #47143)
JS module fetching failures can now be retried (@Gae24, #46919)
KeyEvent.keyCode values for many nonprintable keys now match other browsers (@eachra-bawn, #47461)
making timing on Performance return a PerformanceTiming object (@jdm, @aniebietafia, #46990)
synthesizing font variations from font-style (@simonwuelker, @mrobinson, #46918, #47364)
the Get Element Tag Name WebDriver command (@yezhizhen, #47216)
removed nonstandard WebDriver-related properties on the global object (@mrobinson, #47542)
sniffing RAR responses correctly (@wood-ghost, #47366)
Attribute nodes created during parsing now have the expected namespace prefix (@Ms2ger, #47030)
improving text-transform: capitalize (@mrobinson, #46910)
zero-sized margins inside of inline boxes (@Loirooriol, #47020)
incorrect buttons values in pointer capture transitions (@steigeo, #45628)
empty lists returned by load() on FontFaceSet (@simonwuelker, #47564)
cancelling more ongoing network requests when performing a navigation (@mrobinson, #47576)
shaping text across inline boxes (@mrobinson, #46829)
scrollable overflow for position: sticky (@rayguo17, #43766)
fixing hyperlinks for blob: URLs (@TimvdLippe, #47226)
firing the error callback for decodeAudioData on BaseAudioContext (@amittenak47, @jdm, #46870)

New contributors

A special thanks to the following people for landing their first patch in Servo:

Frans Skarman (@TheZoq2, #46938)
Moamen Hesham (@moamenhesham0, #47391)
Miles Wirht (@philocalyst, #46996)
Vaibhav Srivastava (@vaibhav8a, #47626)
wood-ghost (@wood-ghost, #47366)
禾可 (@Lfan-ke, #47514)

Interested in helping build a web browser? Take a look at our curated list of issues that are good for new contributors!

Donations

Thanks again for your generous support! We are now receiving 8128 USD/month (+3% from July) in recurring donations. This helps us cover the cost of our speedy CI and benchmarking servers, one of our latest Outreachy interns, and funding maintainer work that helps more people contribute to Servo.

Servo is also on thanks.dev, and already 36 GitHub users (+1 from July) that depend on Servo are sponsoring us there. If you use Servo libraries like url, html5ever, selectors, or cssparser, signing up for thanks.dev could be a good way for you (or your employer) to give back to the community.

8128 USD/month

10000

Your Donations at Work: One Year of Sponsored Servo Development

2026-09-15T00:00:00Z

Last September, the Servo project announced that long-time maintainer Josh Bowman-Matthews (@jdm) would work part-time on improving the Servo contributor experience, entirely funded by the monthly donations on OpenCollective and GitHub. In his own words, here is a look back over the past year!

First of all, I am enormously grateful to everyone who financially supports Servo, as those donations have enabled me to devote significant time to a project that I care a lot about. Some highlights from that funded work that I’m proud of:

I nominated 8 new maintainers
I reviewed 1150 pull requests
I filed 114 issues targeted at newer contributors (92% of them have been fixed)
I wrote new documentation about borrow hazards, experimental features, the AI policy, finding things to do, and fixing stable and intermittent test failures

On top of that, I spent time diagnosing unexpected failures in others’ PRs and fixed numerous intermittent test failures that made merging PRs more difficult for everyone.

A few pieces of work from this period that stand out to me:

supporting a large scale rewrite of Servo’s JS engine integration to address intermittent panics related to garbage collection—I reviewed lots of pull requests, but also filed many issues that enabled the work addressing the panics to be spread across many other contributors
getting tagged in to help understand test failures, uncovering our broken window.open behaviour, and eventually making a lot of flaky tests more stable
supporting another contributor’s grant proposal to work on Servo that was approved!

This role I’ve carved out means a lot to me—I’ve found a healthy balance that allows me to spend time with my family as well as make meaningful contributions to Servo, and I get to spend a lot of time looking for ways to make the project more accessible for others. A big thank you to everybody supporting the project and my work; each individual monthly donation makes a big difference! I’m excited to see what’s possible in the coming year.

July in Servo: more platforms, faster canvas, web fonts in SVG, and more!

2026-08-31T00:00:00Z

Servo 0.5.0 contains all of the changes we landed in July, which came out to 488 commits, and we now publish binaries for Linux aarch64 (@mukilan, #46760)!

DOM text selections are now visible (@mrobinson, @SimonSapin, #46698, #46864, #46742, #46889, #46126). Interactive selection is coming soon!

For security fixes, see § Security.

`, and DOM selection rendering" />

We’ve shipped several new web platform features:

‘Cache-Control: stale-while-revalidate’ (@arayaryoma, #46060)
‘text-decoration-thickness’ (@nicoburns, #46592)
‘box-decoration-break’, for the most part (@Psychpsyo, #45492)
‘@font-feature-values’, for the most part (@simonwuelker, #45308)
‘font-language-override’, for the most part (@simonwuelker, #46618)
‘font-variant-alternates’, for the most part (@simonwuelker, #45308)

Plus a bunch of new DOM APIs:

Ed448, X448, and KMAC algorithms in SubtleCrypto (@kkoyung, #46402, #46141, #46180, #46583, #46606, #46622, #46334, #46376)
‘insertHorizontalRule’, ‘insertImage’, ‘insertText’, and ‘forwardDelete’ commands in document.execCommand() (@Psychpsyo, #46608, #46597, #46538, #46838)
AnimationEffect (@simonwuelker, #46677)
new Touch() (@yezhizhen, #46741)
duplex property on Request (@Taym95, #46858)
effect property on Animation (@simonwuelker, #46677)
getKeyframes() and setKeyframes() on KeyframeEffect (@simonwuelker, #46118)
id property on LargestContentfulPaint (@shubhamg13, #46828)
read-only CSSFontFeatureValuesRule (@simonwuelker, #46728)

This is another big update, so here’s an outline:

You can help!

If you’re working on a pull request that you think might be interesting for the next monthly update, even if you’re not 100% sure, tell us about it by following the steps below:

You add the monthly update label to your pull request, or comment @servo-highfive monthly update
Highfive posts a comment asking you some questions
You answer those questions in a comment containing @servo-highfive monthly update answer

Security

Servo was potentially affected by vulnerabilities in quick-xml and crossbeam-epoch that have been fixed in Servo 0.5.0 (@atouchet, @Loirooriol, #46737, #46324). For more details, see RUSTSEC-2026-0194, RUSTSEC-2026-0195, and RUSTSEC-2026-0204.

We’ve updated ANGLE from a version based on Firefox 115.x ESR (02755361e26d8) to a version based on Firefox 140.12.0 ESR (f8025617e815f), which likely includes many security fixes (@jschwe, @sagudev, #46455, mozangle#100).

Real world compat

The duck on the DuckDuckGo (duckduckgo.com) landing page now renders in v0.5.0, after we fixed a preload bug that affected SVG images (@jdm, #46668).

v0.4.0

v0.5.0

duckduckgo.com

Most of Gumroad (gumroad.com), except for the landing page, did not render at all in v0.4.0, but as of v0.5.0, pages like the Discover page or this product page render almost perfectly.

v0.4.0

v0.5.0

gumroad.com

v0.4.0

v0.5.0

gumroad.com

We’re interested to hear how well your favourite websites run in Servo! Report successes in this Zulip thread, and failures in our GitHub issues.

Work in progress

The upgrade to Stylo 2026-07-01 brings several changes to built-in CSS functions (@Loirooriol, #46129):

‘alpha()’ is now supported, under --pref layout_css_alpha_color_function_enabled
‘progress()’ is now supported, under --pref layout_css_progress_function_enabled
‘ellipse()’ values ‘closest-corner’ and ‘farthest-corner’ are no longer stable due to spec uncertainty, but they are still experimental, under --pref layout_css_ellipse_corners_enabled
‘attr()’ is more conformant, under --pref layout_css_attr_enabled

WebGPU content can now enjoy better conformance and use GPUExternalTexture and importExternalTexture() on GPUDevice, under --pref dom_webgpu_enabled (@sagudev, #45873, #46178, #46286).

IndexedDB content can now use the name property on IDBIndex, under --pref dom_indexeddb_enabled (@skyz1, #45512).

document.fonts now includes a FontFace for each valid ‘@font-face’, under --pref dom_fontface_enabled (@simonwuelker, #46509, #46537).

All of the features above are enabled in servoshell’s experimental mode.

We’ve started implementing WebVTT for native subtitles and captions, enabled by default (no --pref). While they don’t render just yet, we can now fetch each <track src>, parse the WebVTT, and expose cues via the track property on HTMLTrackElement (@TimvdLippe, #46289, #46383).

July was a big month for accessibility in Servo, under --pref accessibility_enabled. The focus for this month has been on performance, with the accessibility tree now supporting incremental updates (@alice, @delan, #45578, #45971, #46589, #46691, #46385), requiring fewer HashMap lookups and tree walks (@alice, @delan, #45798, #46740, #46348), and allowing for faster DOM mutations (@alice, #46348, #46530).

We’ve also started working on the File and Directory Entries API, to allow users to select and upload entire directories via <input type=file> and drag-and-drop. To that end, we now have webkitGetAsEntry() on DataTransferItem, plus minimal support for FileSystemEntry, FileSystemDirectoryEntry, and FileSystemFileEntry, under --pref dom_entries_api_enabled (@yezhizhen, #46456, #46879, #46832).

Embedding API

We’ve improved the docs for the servo crate, and for WebViewDelegate (@mukilan, #46193).

Breaking change: ServoBuilder::webxr_registry() has been removed. Instead use the new Servo::register_webxr_registry, which is a lazy design that has allowed servoshell to halve its startup time (@Narfinger, #46494).

For users and developers

servoshell for Android now runs on Android 10+ (91% market share), not just Android 13+ (68% market share), improving adaptability and reducing waste (@jschwe, #46142, #46308). We’ve also fixed a problem with building for Android on macOS (@jschwe, #46128).

servoshell for Windows is now better behaved when run in a console window, making the command prompt wait until servoshell exits (@yezhizhen, #43010).

When using the Firefox DevTools, the Console tab now supports some basic autocomplete (@freyacodes, #46382).

We’ve finished modernising servoshell for Android to use Compose UI (@veyndan, #46085, #46164, #46253, #46257, #46317, #46353, #46565, #46612, #46626, #46666, #46663, #46700), and we’re now migrating Servo as a library to use Kotlin (@veyndan, #46817, #46895, #46772).

More on the web platform

Inline SVG can now use web fonts defined in the containing page (@yodalee, #45979). We’re also implementing the SVG DOM, starting with stub interfaces for SVGElement, SVGCircleElement, SVGDefsElement, SVGEllipseElement, SVGLineElement, SVGLinearGradientElement, SVGPathElement, SVGPolygonElement, SVGPolylineElement, SVGRadialGradientElement, SVGStopElement, SVGRectElement, SVGSymbolElement, and SVGUseElement (@mu-mostafa98, #46558).

<button> now vertically centers its contents (@Loirooriol, @mrobinson, #46590), and behaves better with ‘display: block’ and ‘display: inline’ (@Loirooriol, #46536).

We’ve improved the conformance of <form> without <form action> (@kevlu93, #46860), <color> values (@Loirooriol, #46129), GamepadEvent (@log101, #46788), document.execCommand(“delete”) (@Psychpsyo, #46539), the selectorText property on CSSStyleRule (@simonwuelker, #46687), and Set Window Rect in WebDriver (@janeoa, #46475, #46477).

We’ve fixed bugs related to <iframe> (@jschwe, @jdm, #46587), <img> (@yodalee, #46892), <textarea> (@SimonSapin, @mrobinson, #46309), custom properties (@Loirooriol, #46129), ‘::before’ and ‘::after’ (@Loirooriol, #46640), ‘flex-direction: column’ (@simonwuelker, #46697), ‘float’ (@Loirooriol, @mrobinson, #46407, #46500, #46505), ‘@font-face’ (@simonwuelker, #46568, #46271, #46436), ‘position: absolute’ (@simonwuelker, #46358, #46637), Blob (@jdm, #46881), IDBDatabase and IDBObjectStore and IDBIndex (@mrobinson, #46615), the adoptedStyleSheets property on ShadowRoot (@simonwuelker, #46738), delete() on FontFaceSet (@simonwuelker, #46634), moveBefore() on Element (@mrobinson, #46599), resizeTo() on Window (@janeoa, #46477), the selected property on HTMLOptionElement (@rhit-kapilaar, #46386), and the value property on HTMLSelectElement (@simonwuelker, #46230).

Performance and stability

2D canvas rendering is now multithreaded, improving frame rates by up to 55% and power consumption per frame by up to 42% (@yezhizhen, #46410), and should use a lot less memory too (@jschwe, @sagudev, #46786).

Text rendering is up to 10x faster for cases with the same text and different ‘font-size’ (@Loirooriol, #46129).

Flex layout benchmarks are up to 3% faster, and an improvement to getElementsByClassName() has made some websites up to 1% faster (@Narfinger, @jdm, #46563, #46595, #46594).

We’ve also reduced memory usage, allocations, GC rooting steps, and other operations in many parts of Servo (@mrobinson, @jdm, @yezhizhen, @Narfinger, @Gae24, @SimonSapin, @Taym95, @cychronex-labs, @arayaryoma, #46499, #46411, #46659, #45974, #46377, #45758, #46440, #46762, #46301, #46349, #46419, #46418, #46420, #46460, #46633, #46638, #46690, #46745, #46726, #46564, #46144, #46664, #46462, #46139, #46430, #46446, #46498, #46548, #46598, #46632, #46656, #46678, #46718, #46722, #46238, #46072, #46408, #46438, #46437, #46528, #46124, #46330, #46412, #46807).

We’ve fixed a crash regression with memory corruption (@mrobinson, #46316), several dynamic-borrow-related crashes (@Narfinger, @SharanRP, @Taym95, @agrawalx, @amittenak47, @sungmen, #46381, #46384, #46405, #46684, #46452, #46770, #46830, #46763), plus crashes related to:

<area> without <area href> (@simonwuelker, #46341)
<progress> or shadow DOM (@mrobinson, @simonwuelker, #46188)
<table> layout (@mrobinson, #46775)
<td rowspan> (@mrobinson, #46841)
<svg> without <svg viewBox> (@Narfinger, @mrobinson, #46199)
<use> in SVG (@mrobinson, @Loirooriol, #46261)
‘animation’ (@mrobinson, @Loirooriol, #46689)
‘content’ (@Loirooriol, @mrobinson, #46314)
‘mix-blend-mode’ (@mrobinson, #45624)
ArrayBuffer (@jdm, #46504)
adoptedStyleSheets on Document (@TimvdLippe, #46373)
execCommand("delete") on Document (@TimvdLippe, #46265)
removing DOM nodes (@SimonSapin, #46866)

We’ve continued our long-running effort to use the Rust type system to make Servo’s integration with SpiderMonkey safer and more reliable (@Gae24, @Narfinger, @TimvdLippe, @jdm, @kunalmohan, @lumiscosity, @simonwuelker, #46191, #46777, #46890, #46243, #46248, #46246, #46310, #46312, #46333, #46147, #46150, #46151, #46229, #46262, #46375, #46374, #46529, #46584, #46585, #46593, #46693, #46166, #46156, #46254, #46267, #46268, #46269, #46270, #46284, #46285, #46318, #46435, #46461).

New contributors

A special thanks to the following people for landing their first patch in Servo:

Umut Cevdet Koçak (@UMCEKO, #46256)
Yash Agrawal (@agrawalx, #46770)
amittenak47 (@amittenak47, #46743)
Apoorva Pendse (@apoorvapendse, #46739)
dDostalker (@dDostalker, #46181)
Oisín Ó Maolchathail (@eachra-bawn, #46478)
Kevin Lu (@kevlu93, #46860)
Mohamed Mostafa (@mu-mostafa98, #45405)
SeongMan Jeon (@sungmen, #46763)
Yoda Lee (@yodalee, #45979)

Interested in helping build a web browser? Take a look at our curated list of issues that are good for new contributors!

Donations

Thanks again for your generous support! We are now receiving 7824 USD/month (+1.8% from June) in recurring donations. This helps us cover the cost of our speedy CI and benchmarking servers, one of our latest Outreachy interns, and funding maintainer work that helps more people contribute to Servo.

Servo is also on thanks.dev, and already 35 GitHub users (same as June) that depend on Servo are sponsoring us there. If you use Servo libraries like url, html5ever, selectors, or cssparser, signing up for thanks.dev could be a good way for you (or your employer) to give back to the community.

7824 USD/month

10000

June in Servo: real world compat, media queries, SharedWorker, and more!

2026-07-31T00:00:00Z

Servo 0.4.0 contains all of the changes we landed in June, which came out to yet another record 558 commits (April: 534, May: 391). For security fixes, see § Security.

We’ve shipped several new web platform features:

‘attr()’, in experimental mode (@Loirooriol, #45041)
‘image(<color>)’, ‘closest-corner’, and ‘farthest-corner’ in ‘ellipse()’ and ‘circle()’ (@Loirooriol, #45421)
‘calc()’ and other mathematical expressions can now be resolved later than parse time, e.g. sign(1em - 32px) (@Loirooriol, #45421)
‘font-feature-settings’ in ‘@font-face’ (@simonwuelker, #45393)
‘@media (device-width)’, ‘@media (device-height)’, ‘@media (height)’, ‘@media (aspect-ratio)’, and their min- and max- variants (@jdm, @mrobinson, @nicoburns, @jschwe, #44978, #45707, #45490)
‘@media (orientation)’ (@nicoburns, #45707)
‘@media (pointer)’ and ‘@media (any-pointer)’ (@nicoburns, #45681)
‘@media (hover)’ and ‘@media (any-hover)’ (@nicoburns, #45681)

Plus a bunch of new DOM APIs:

SharedWorker (@Taym95, #45786)
console.dir() (@Taym95, #45109)
customElementRegistry on Document and ShadowRoot (@shubhamg13, #45872)
initialize() on CustomElementRegistry (@shubhamg13, @yezhizhen, #45903)
new CustomElementRegistry() (@shubhamg13, #45791, #45550)
textStream() on Request, Response, and Blob (@yezhizhen, #45864, #45861)
setPointerCapture(), releasePointerCapture(), hasPointerCapture() on Element (@webbeef, #45048)
ontouchstart, ontouchend, ontouchmove, ontouchcancel on Element (@stevennovaryo, #45049)
crypto.subtle.digest() for KT128 and KT256 (@kkoyung, #45699)
crypto.subtle.getPublicKey() for ML-KEM and ML-DSA (@kkoyung, #45252)

This is another big update, so here’s an outline:

You can help!

Servo is steadily becoming a bigger and busier project every month, and by June 2026, we’ve been reading through over four times the commits as we did when we started in September 2023.

This is hard work, particularly since there are things we need to know that are often difficult to answer just by reading the changes:

Who does the change affect, if anyone? Does it affect users, Servo developers, embedders, or some other group?
What observable difference does the change make, if any?
Does the feature require any preferences to be enabled, or is it enabled for everyone by default?
Are any real-world websites affected by the change?
What issue or broader project is the change related to? This question is answered by Fixes: #xxxxx or Part of: #xxxxx in the PR description.

Thanks to an initiative by @jdm, it’s now easier than ever for you to help us answer those questions, using the Servo Highfive bot! If you’re working on a pull request that you think might be interesting for the next monthly update, even if you’re not 100% sure, tell us about it by following the steps below:

You add the monthly update label to your pull request, or comment @servo-highfive monthly update
Highfive posts a comment asking you some questions
You answer those questions in a comment containing @servo-highfive monthly update answer

Security

Servo’s JS runtime, SpiderMonkey 140.10.1, had several security bugs that have been fixed in Servo 0.4.0 with the update to SpiderMonkey 140.11.0 (@jschwe, #45584). For more details, see CVE-2026-8388, CVE-2026-8391, CVE-2026-8974, CVE-2026-8975, and MFSA 2026-48.

Several more security bugs in Servo’s JS runtime have been fixed in Servo 0.4.0 with the update to SpiderMonkey 140.12.0 (@jschwe, #45766). The exact CVEs that apply to us are not yet known, but for more details, see MFSA 2026-58.

RSA operations in SubtleCrypto now do modular exponentiation in constant time (@kkoyung, #45631). Please note that our RSA implementation is currently vulnerable to the Marvin Attack – for more details, see RUSTSEC-2023-0071.

ML-DSA operations in SubtleCrypto now do the Decompose step in constant time, fixing RUSTSEC-2025-0144 (@kkoyung, #45294).

We’ve fixed an HTML injection bug (XSS) in file:/// directory listings, which affected file names containing </script> (@sahvx655-wq, #45510).

Real world compat

Layout correctness has significantly improved on lichess.org, and many websites have become a lot more readable thanks to our improved handling of variable fonts (@simonwuelker, #45768), including Zulip (servo.zulipchat.com) and Speedtest (speedtest.net).

v0.3.0

v0.4.0

lichess.org

v0.3.0

v0.4.0

Zulip (servo.zulipchat.com)

v0.3.0

v0.4.0

Speedtest (speedtest.net)

Many websites worked in Servo even before version 0.4.0, including Google Photos (photos.google.com) and Cash Converters (cashconverters.com.au), and continue to work in version 0.4.0. Other websites, like Google Maps (maps.google.com) and OpenStreetMap (www.openstreetmap.org), render well but have some issues with interactivity.

Google Photos (photos.google.com)

Cash Converters (cashconverters.com.au)

Google Maps (maps.google.com)

OpenStreetMap (www.openstreetmap.org)

We’re interested to hear how well your favourite websites run in Servo! Report successes in this Zulip thread, and failures in our GitHub issues.

Work in progress

We’re implementing the more powerful version of ‘attr()’ that can be used anywhere, not just in ‘content’, under --pref layout_css_attr_enabled (@Loirooriol, #45041, #45421, #45495, #45752).

WebGPU support has improved, under --pref dom_webgpu_enabled:

implemented copyExternalImageToTexture() on GPUQueue (@sagudev, #45646)
implemented createQuerySet() on GPUDevice and resolveQuerySet() on GPUCommandEncoder (@sagudev, #45644)
implemented pushDebugGroup(), popDebugGroup(), and insertDebugMarker() on GPUCommandEncoder, GPUComputePassEncoder, and GPURenderPassEncoder (@jschwe, #45489)
more conformant GPUTexture (@sagudev, #45300)
more conformant requestAdapter() on GPU (@sagudev, #45424)
more conformant secure context enforcement (@sagudev, #45279)

All of the features above are enabled in servoshell’s experimental mode.

We’ve made more progress towards accessibility support, under --pref accessibility_enabled (@alice, @delan, #45555, #45554, #44949).

We’ve started implementing visible and interactive text selection (@mrobinson, @SimonSapin, #46107), one of the most long-awaited features of any web browser. Stay tuned!

We’ve also started working on Web Animations, under --pref dom_web_animations_enabled (@simonwuelker, #45522, #45983), as well as webkitRelativePath on File, under --pref dom_entries_api_enabled (@yezhizhen, #45666).

Rust doesn’t have a stable ABI, so it has generally not been possible to embed Servo in another application without building Servo from source. To make it possible, we’ve started designing a wrapper C API that will let you consume Servo as a prebuilt shared library using the stable and ubiquitous C ABI (@mukilan, #44984). Eventually the idea is that we’ll create a wrapper Rust API around that wrapper C API, so you can have both the ergonomics of Rust and the build simplicity of C.

Embedding API

New in the Servo API:

WebView::rendering_context (@mrobinson, #46047)

Breaking changes:

WebView::send_error has been removed (@mukilan, #45502) – this method was always meant to be internal, and has become unused after we introduced the new WebView- and WebViewDelegate-based API

We’ve improved the docs for WebView, WebViewDelegate, JSValue, AlertDialog, AllowOrDenyRequest, AuthenticationResponse, BluetoothDeviceDescription, ConfirmDialog, ConsoleLogLevel, CreateNewWebViewRequest, EmbedderControl, EmbedderControlResponse, FilePicker, Image, JavaScriptErrorInfo, NavigationRequest, PermissionRequest, PixelFormat, PromptDialog, ProtocolHandlerRegistration, ProtocolHandlerUpdateRegistration, Scroll, SelectElement, SelectElementRequest, and WebViewVector (@mukilan, #45282, #45467).

For users and developers

In servoshell:

the Android version now requires Android 13+ (@jschwe, #46104)
the desktop version now lets you drag and drop files to open them (@simonwuelker, #45454)
the desktop version now lets the tab bar scroll horizontally if you have too many tabs open, but from one tab hoarder to another, maybe you should reconsider having so many tabs open (@Nylme, #44884)
the desktop version enters fullscreen on the monitor containing the window, even if you’ve moved it to a different monitor (@rhit-kapilaar, #45556)
the desktop UI is more performant, resizes more smoothly, and no longer gets stuck in hovered states (@mrobinson, #45289, #45456, #45290)
<select multiple> should now be interactable on all desktop platforms (@alexcat3, #45419)
localhost:<port> now implies http:// in the location bar and on the command line, rather than treating localhost: as an unsupported URL scheme (@SteveSharonSam, #45729, #45832)

When using the Firefox DevTools:

in the Console tab, uncaught exceptions are reported correctly (@jdm, #45549)
in the Console and Debugger tabs, you can now inspect the elements of nested arrays and the entries of Map objects (@atbrakhi, #45435, #45514, #45767)
in the Debugger tab, the Scopes panel now shows any ‘(uninitialized)’ variables, the value of this, and the global scope (@atbrakhi, @eerii, #45824, #45517)

We’ve fixed some build issues on riscv32, riscv64, and arm64 (@fxzjshm, @saschanaz, #45285, #45731), and modernised servoshell for Android to use Compose UI and Kotlin (@veyndan, #45923, #45932, #45941, #45982, #45985, #46015, #46035, #46037, #46046, #46053, #46061, #46071, #45641, #45643, #45650, #45665, #45671, #45676, #45679, #45683, #45712, #45713, #45734, #45738).

For developers of Servo itself:

mach try --help now lists all of the kinds of try jobs you can run (@shubhamg13, #45607)
mach test-wpt --update-expectations lets you run Web Platform Tests and update expectations in a single command (@TimvdLippe, #45521), rather than having to run mach test-wpt --log-raw <path> followed by mach update-wpt <path>

More on the web platform

To allow for more performant scrolling, ‘wheel’ events are no longer .cancelable unless there are one or more non-passive event listeners (@kunalmohan, #45667). Note that like in Firefox, ‘wheel’ events are passive by default.

‘dotted’, ‘dashed’, and ‘wavy’ text decorations are now continuous across element boundaries (@mrobinson, #45726).

We’ve improved the conformance of <dialog> (@skyz1, @mrobinson, #45825, #45761), <iframe sandbox> (@cychronex-labs, #45880), <input minlength> and <input maxlength> (@skyz1, #45705), CSS gradients (@mrobinson, #43945), ‘font-style’ and ‘unicode-range’ in ‘@font-face’ (@Loirooriol, #45821), FontFaceSet (@mrobinson, #45390, #45382), HTMLInputElement (@steigeo, #45416), IntersectionObserver (@jdm, #45655, #45659, #45680), new Response() (@yezhizhen, #45953), URL.createObjectURL() and URL.revokeObjectURL() (@yezhizhen, #45182, #45417), and ECDSA and Ed25519 in SubtleCrypto (@kkoyung, #45833, #46017).

We’ve fixed bugs related to <input hidden> (@mrobinson, #45750), ‘animation-delay’ (@yezhizhen, #45013), ‘clip-path’ (@Loirooriol, #45468, #45373), ‘tab-size’ (@SimonSapin, @mrobinson, #45309), ‘width’ and ‘height’ (@RichardTjokroutomo, #44627), ‘box-shadow: inset’ (@Loirooriol, #45620), ‘animationiteration’ events (@Loirooriol, #45990), ‘click’ events (@mrobinson, #45751), ‘load’ events (@jdm, #45883), ‘error’ events in Worker global scopes (@Gae24, #45829), and document.getElementById() (@mrobinson, #45433).

Garbage collection safety

We use a RefCell-based mechanism to store many of our DOM types in other DOM types, enforcing Rust’s “aliasing xor mutability” rule at runtime by panicking if the rule is violated. But when garbage collection happens, we need to borrow() each DomRefCell to trace the references, and this is the source of many panic bugs. To fix that whole class of bugs, we initially created CanGc, a marker type that would annotate the code paths where GC can occur, in conjunction with custom static analysis (@jdm, #33140).

With the Rust type system we can do even better, if we flip that around and require any borrow_mut() call to prove that GC can not occur by passing a NoGC marker value. We can then require that a &NoGC must be borrowed from a &JSContext (which blocks GC) and not a &mut JSContext (which allows GC), taking advantage of how Rust references work without needing any custom static analysis.

We have a large codebase that needs to be migrated in parts, so for now we’ve created the new method safe_borrow_mut() (@sagudev, #46050). We also need to update all of our script-related code to borrow our safe JSContext wrapper, rather than creating an owned JSContext on the spot.

This continues our long-running effort to use the Rust type system to make Servo’s integration with SpiderMonkey safer and more reliable (@Gae24, @Keerti707, @Narfinger, @TimvdLippe, @sagudev, @guptapiyush16, @ivomurrell, @kunalmohan, @skyz1, #45230, #45436, #45503, #45617, #45711, #45797, #45800, #45858, #45884, #45937, #45902, #45968, #45977, #45991, #46003, #46005, #46084, #45548, #45552, #45590, #45909, #45912, #45943, #46089, #46117, #46114, #45320, #45324, #45328, #45340, #45381, #45385, #45410, #45392, #45409, #45604, #45616, #45618, #45627, #45636, #45662, #45663, #45675, #45674, #45677, #45684, #45735, #45807, #45810, #45816, #45818, #45828, #45838, #45836, #45837, #45840, #45841, #45857, #45859, #45862, #45875, #45887, #45931, #45964, #45935, #45987, #45988, #46001, #46040, #46051, #46057, #46106, #46125, #45678, #46002, #45845, #45645, #45673, #45259, #45817, #45822, #45876, #45877, #45891).

Performance and stability

NoGC was designed to prevent dynamic borrow failures, but it also enables some performance optimisations! If we can prove that garbage collection is impossible in some part of Servo, we can often avoid rooting JavaScript objects when interacting with them within that region of code. This has allowed us to reduce overheads by over 1% in the layout process and in HTMLCollection (@Narfinger, #46092, #45582).

Our memory usage has improved, with BoxFragment now 17% smaller (288 → 240 bytes on amd64) and ShapeCacheEntry now smaller too (@SimonSapin, @mrobinson, @simonwuelker, #45183, #45496).

We’ve fixed some nasty memory leaks when reloading and in 2D canvases (@Taym95, @sagudev, @jschwe, #45455, #45261, #45414).

Speaking of which, 2D canvases now use up to 23% less power (@yezhizhen, #45301), and we now avoid rasterising the same SVG more than once (@Narfinger, @jschwe, #44805).

Servo now decodes all images asynchronously and fills image caches asynchronously, leaving script threads (web content processes) more time for other work (@Narfinger, #45542, #44483). On top of that, we’ve improved incremental layout (@mrobinson, @Loirooriol, #45411) and reduced reflows in IntersectionObserver (@jschwe, #45986).

We’ve started working on incremental updates for the stacking context tree, and as a side effect, we’ve made some layout-bound microbenchmarks up to 10% faster (@mrobinson, @Loirooriol, #45208).

We’ve also reduced allocations, copies, GC rooting steps, and other operations in many parts of Servo (@Narfinger, @SimonSapin, @mrobinson, @Loirooriol, #45506, #45969, #45940, #45760, #46090, #45335, #45413, #45511).

For several months, Frédéric (@fred-wang) has been fuzzing for Servo bugs, and thanks to his work we’ve fixed sixteen (16) crash bugs in June, affecting <iframe>, <slot>, <link onerror>, ‘animation’, ‘clip-path’, ‘content’, ‘rotate’, ‘transition’, ‘transform-style’, ‘display: contents’, ‘overflow: clip’, CSSKeyframesRule, FontFace, stop() on Window, document.elementFromPoint(), and the DOM tree (@mrobinson, @Loirooriol, @fred-wang, #46031, #46027, #46054, #46058, #46016, #46028, #46033, #45287, #45951, #45634, #45629, #46110, #46094, #45799, #45611, #45682, #45788, #45612, #45834).

We’ve also fixed crash bugs related to IPC failures, HTMLInputElement, Range, the DevTools Debugger tab, and when servoshell is built with --features native-bluetooth (@jschwe, @Taym95, @mrobinson, @atbrakhi, @mukilan, #45311, #45619, #45765, #45513, #45702).

New contributors

A special thanks to the following people for landing their first patch in Servo:

Deepam Goyal (@Deepam02, #44836)
Mark (@Mark-Boger, #45486)
Mr SheerLuck (@MrSheerluck, #45557)
Psychpsyo (Cameron) (@Psychpsyo, #45494)
TusharSariya (@TusharSariya, #43663)
Adam Sharif (@adamsharifc, #45551)
Akash Ravikumar (@ak4shravikumar, #45736)
Sean Cunneen (@alexcat3, #45419)
Abdul Wahab Melethil Shibu (@cychronex-labs, #45880)
darkdragon-001 (@darkdragon-001, #45267)
Frédéric Wang Nélar (@fred-wang, #45834)
fxzjshm (@fxzjshm, #45285)
Piyush Gupta (@guptapiyush16, #45845)
Ivo Murrell (@ivomurrell, #45645)
rhit-kapilaar (@rhit-kapilaar, #45556)
sahvx655-wq (@sahvx655-wq, #45510)
Kagami Sascha Rosylight (@saschanaz, #45731)
shangguanmachine-dot (@shangguanmachine-dot, #45310)
Glenn Skrzypczak (@skyz1, #45471)
Oskar Steiger (@steigeo, #45416)
Veyndan Stuart (@veyndan, #45326)

Interested in helping build a web browser? Take a look at our curated list of issues that are good for new contributors!

Donations

Thanks again for your generous support! We are now receiving 7681 USD/month (+0.2% from May) in recurring donations. This helps us cover the cost of our speedy CI and benchmarking servers, one of our latest Outreachy interns, and funding maintainer work that helps more people contribute to Servo.

Servo is also on thanks.dev, and already 35 GitHub users (same as May) that depend on Servo are sponsoring us there. If you use Servo libraries like url, html5ever, selectors, or cssparser, signing up for thanks.dev could be a good way for you (or your employer) to give back to the community.

7681 USD/month

10000

May in Servo: user scripts, mp4 compat, blackboxing in DevTools, and more!

2026-06-30T00:00:00Z

Servo 0.3.0 contains all of the changes we landed in May, which came out to 391 commits (April: 534). For security fixes, see § Security.

We’ve shipped several new web platform features:

‘font-kerning: none’ (@simonwuelker, #44634)
‘font-variant-east-asian’ (@simonwuelker, #44989)
‘font-variant-ligatures’ (@simonwuelker, #44903)
‘font-variant-numeric’ (@simonwuelker, #44950)
‘font-variant-position’ (@simonwuelker, #45142)
mp4 files without fast start in <video> (@calvaris, #45084)
<form enctype="multipart/form-data"> (@yezhizhen, #45028)
<form enctype="text/plain"> (@yezhizhen, #45111)
<![CDATA[]]> layout (@mrobinson, #44791)

Plus a bunch of new DOM APIs:

onslotchange property on ShadowRoot (@jdm, #44688)
screenLeft and screenTop on Window (@TG199, #45128)
new Blob() with {endings: "native"} (@yezhizhen, #44803)
new PerformanceMark() (@shubhamg13, #44702)
parseHTML() on Document (@kkoyung, #44952)
readAsBinaryString() on FileReader (@yezhizhen, #44858, #44921)
performance.measure() with mark values ‘redirectStart’, ‘redirectEnd’, ‘secureConnectionStart’, and ‘responseEnd’ (@shubhamg13, #44673, #44624, #44850, #44739)

We’ve also fixed some build issues on Windows (@mukilan, #45079), FreeBSD (@delan, @mrobinson, @mukilan, #44600), and for anyone building Servo on NixOS or with Nix (@freyacodes, #45051, #45135).

This is another big update, so here’s an outline:

Security
– memory safety fixes
Work in progress
– execCommand(), Sanitizer, IndexedDB, accessibility, workers
Embedding API
– MSRV, cookies, preferences, diagnostics
For users and developers
– --host-file, --userscripts, DevTools Debugger
More on the web platform
– focus, forms, navigation, SubtleCrypto, WebGPU
Performance
– about:memory, threads, layout, DOM, build times
Stability
– crashes, hangs, static analysis

Security

Servo’s JS runtime, SpiderMonkey 140.10.0, had several memory safety bugs that have been fixed in Servo 0.3.0 with the update to SpiderMonkey 140.10.1 (@jschwe, #44755). For more details, see CVE-2026-7322, CVE-2026-7323, and MFSA 2026-36.

Work in progress

We’re continuing to implement document.execCommand() for rich text editing, under --pref dom_exec_command_enabled (@TimvdLippe, #44735, #44973, #44887). This release adds support for the ‘backColor’, ‘foreColor’, ‘createLink’, ‘unlink’, ‘superscript’, ‘subscript’, and ‘removeFormat’ commands (@TimvdLippe, #44644, #44682, #44657, #44710, #44677), plus partial support for the ‘insertParagraph’ command (@TimvdLippe, #44909).

We’re also working on the Sanitizer API, under --pref dom_sanitizer_enabled. With the feature now enabled in servoshell’s experimental mode (@kkoyung, #44701), this release adds support for setComments(), setDataAttributes(), allowProcessingInstruction(), removeProcessingInstruction(), and removeUnsafe() on Sanitizer (@kkoyung, #44734, #44983).

IndexedDB continues to improve, under --pref dom_indexeddb_enabled. This release brings a more conformant abort() on IDBTransaction (@Taym95, #43950).

All of the features above are enabled in servoshell’s experimental mode.

We’ve made more progress towards accessibility support, under --pref accessibility_enabled. This includes the name from contents algorithm (@alice, @delan, @mrobinson, #44439) and several changes towards building the accessibility tree incrementally (@alice, @delan, @mrobinson, #44766, #45035, #45207, #44768, #44785, #44801, #44767, #45029). The latter is critical for performance in real-world web content.

We’re now working on SharedWorker and ServiceWorker, under --pref dom_sharedworker_enabled and --pref dom_serviceworker_enabled respectively. This release adds support for new SharedWorker() (@Taym95, #44761), and parts of the ServiceWorker API (@gterzian, @arihant2math, #45082, #44787).

Embedding API

Servo now requires Rust 1.88.0 or newer, up from the old MSRV of 1.86.0 (@sagudev, #44815). We run compile tests with the MSRV, but most of our testing is now done with Rust 1.95.0 (@simonwuelker, #44632).

Breaking changes to the cookies methods in our SiteDataManager API (@longvatrong111, #44708):

SiteDataManager::clear_cookies now takes an additional callback argument, allowing it to be called async – to continue calling it sync, pass None as the callback
SiteDataManager::clear_session_cookies now takes an additional callback argument, allowing it to be called async – to continue calling it sync, pass None as the callback
SiteDataManager::set_cookie_for_url now takes an additional callback argument, allowing it to be called async – to continue calling it sync, pass None as the callback
SiteDataManager::set_cookie_for_url_async has been removed in favour of set_cookie_for_url – to migrate, replace set_cookie_for_url_async(callback) with set_cookie_for_url(Some(Box::new(callback)))

Breaking changes to our Preferences API (@Narfinger, @mrobinson, #44307):

threadpools_image_cache_workers_max, threadpools_indexeddb_workers_max, and threadpools_webstorage_workers_max have been removed in favour of a combined thread_pool_workers_max
threadpools_fallback_worker_num has been renamed to thread_pool_fallback_workers
threadpools_async_runtime_workers_max has been renamed to thread_pool_async_runtime_workers_max
threadpools_webrender_workers_max has been renamed to thread_pool_webrender_workers_max

We’ve also reworked our DiagnosticsLogging API (@mukilan, #44703):

You can now set options with DiagnosticsLogging::toggle_option, and check if they are enabled with DiagnosticsLogging::is_enabled
Each option is a variant of DiagnosticsLoggingOption, a new type that also has useful methods for exposing these options in embedder UI
(Breaking change) DiagnosticsLogging no longer has pub fields representing each option – to migrate, replace field writes and field reads with toggle_option and is_enabled respectively
(Breaking change) DiagnosticsLogging::extend_from_string no longer accepts a help option – this option only existed to support servoshell’s -Z help / --debug=help option, so the code implementing it has been moved to servoshell

For users and developers

servoshell has two new options:

You can now configure the path to a hosts file with --host-file= (singular), as an alternative to the HOST_FILE (singular) environment variable (@jschwe, #44880).
You can now provide a directory of user scripts to run in every document with --userscripts= (@jdm, #44754).

When using the Debugger tab in the Firefox DevTools:

You can now “blackbox” a script by clicking Ignore source (@freyacodes, #44359). This prevents breakpoints from being hit inside that script, and it should also allow you to step through execution in the debugger without pausing inside that script.
The Scopes panel is more accurate now (@atbrakhi, @eerii, #44765).

For developers of Servo itself, please note that per project policy, you must not use the output of large language models or other generative AI tools in your contributions. To help us enforce that, we now have CI checks that reject AI agents as coauthors (@SimonSapin, @delan, #44723).

We’ve also fixed build issues with --features vello (@Gae24, @yezhizhen, #44875, #45036).

More on the web platform

We’ve improved the default appearance of <dl>, <ol>, <ul>, <table>, <thead>, <tbody>, <tfoot>, <tr>, <td>, <th>, <dir>, <menu>, and <form> (@avis137, #44837, #44920).

CryptoKey is now serializable, allowing it to be used in structuredClone() and postMessage() (@kkoyung, #45163).

We’ve improved JS error messages in several parts of the DOM (@n0blenote, @jdm, @TG199, @PuercoPop, #44704, #45186, #44656).

We’ve improved the conformance of form submission (@yezhizhen, #44943, #44953, #44954, #44957), tab navigation (@mrobinson, #44684), javascript: url navigation (@jdm, @TimvdLippe, #43490), ‘Refresh’ headers and <meta http-equiv=Refresh> (@jschwe, @mrobinson, #45113, #45116), ‘line-break: anywhere’ (@mrobinson, @SimonSapin, #44609), assign() on Location (@TG199, @jdm, #44298), crypto.subtle.deriveBits() (@kkoyung, #44706), getComputedStyle() (@Loirooriol, #44856), performance.measure() (@shubhamg13, #44675), readAsDataURL() on FileReader (@yezhizhen, #44897, #44924), stream() on Blob (@Taym95, #45133), and ML-KEM in SubtleCrypto (@kkoyung, #45153).

We’ve also landed improvements to GPUSupportedLimits (@sagudev, #45114), GPUTexture (@sagudev, #45154), createBindGroup() on GPUDevice (@sagudev, #45140), and other WebGPU features (@sagudev, #45097).

We’ve fixed bugs related to <svg> with ‘Content-Security-Policy’ (@TimvdLippe, @jdm, #44974), ‘:active’ (@SharanRP, @mrobinson, #43953), ‘:hover’ (@SharanRP, @mrobinson, #43979), ‘align-items’ (@yezhizhen, #44396), ‘border-image-outset’ (@lumiscosity, #45039), ‘padding’ with ‘overflow: scroll’ (@stevennovaryo, #44263), ‘pointerup’ events (@mrobinson, #44666), ‘slotchange’ events (@jdm, #44688), dynamic import() (@Gae24, #44741), and clip() on CanvasRenderingContext2D (@yezhizhen, #44831).

Performance

We’ve built a tool that will help us improve ‘about:memory’ by finding untracked allocations (@jdm, @TimvdLippe, @webbeef, #44674, #44980).

Servo now requires fewer OS threads per CPU, after we combined the thread pools for the image cache, web storage, and IndexedDB (@Narfinger, @mrobinson, #44307).

We’ve landed a bunch of layout optimisations:

The fragment tree is now immutable for the most part, with small pockets of interior mutability where mutability is needed. This means that most fragment tree accesses no longer have to incur the runtime cost of borrowing an AtomicRefCell (@mrobinson, @Loirooriol, #44849).
Two steps in the layout process, calculating containing blocks and building the stacking context tree, require traversing the fragment tree. This can be expensive, but we’ve now combined them into a single fragment tree traversal in most cases (@SimonSapin, @mrobinson, #44911, #45210).
Another step in the layout process, calculating scrollable overflow, used to require traversing the entire fragment tree. We’ve effectively eliminated that traversal, by making the calculation both lazy and incremental (@mrobinson, @Loirooriol, #44854).
We’ve improved the caching of fragments, shaping results, and other layout results between reflows (@mrobinson, @Loirooriol, @SimonSapin, #45038, #44769).
We’ve made incremental fragment layout more precise (@Loirooriol, @mrobinson, #44925).
We’ve reduced the memory usage of text shaping (@mrobinson, @SimonSapin, #44609).

DOM attributes are much more efficient in this release:

When scripts write attribute values, we avoid serialising them until the attribute is read back by a script (if ever), speeding up frequent writes to inline styles by up to 25% (@mrobinson, #44931).
When we parse attributes in HTML or read attribute values internally, we avoid constructing Attr nodes until a script actually needs them, reducing memory usage and making garbage collection less likely (@webbeef, @TimvdLippe, @mrobinson, #44209, #45023, #45031, #45060).

We’ve eliminated a traversal of the whole DOM tree whenever an <iframe> is attached to the tree, which is especially noticeable when parsing documents with many <iframe> tags (@mrobinson, #45236).

Stylesheet locks now use AtomicRefCell, which is even more efficient than a parking_lot::RwLock (@mrobinson, #44883).

On OpenHarmony, we now have a real refresh driver for reduced idle CPU usage (@jschwe, @yezhizhen, #44927), and we now cache the font list on disk for faster startup (@RichardTjokroutomo, @d-desyatkin, #44158).

We’ve also reduced allocations, GC rooting steps, and other operations in many parts of Servo (@jschwe, @kkoyung, @mrobinson, @SteveSharonSam, @Narfinger, @jdm, @nodelpit, @simonwuelker, #44961, #44944, #44972, #45231, #45078, #44662, #44679, #44967, #44963, #44933, #44935, #44905).

To improve Servo’s build times, we’re moving more code out of our massive script crate (@Narfinger, @jdm, #44598, #44636, #44823), and reduced the size of our dependency tree (@jschwe, #44818).

Stability

Several crashes and hangs have been fixed:

in ‘content’ (@mrobinson, @Loirooriol, @SimonSapin, #45227, #44762)
in MediaStream (@jdm, #44781)
in item() on attributes on Element (@webbeef, #44721)
in appendRule() on CSSKeyframesRule (@mrobinson, #45173)
in initEvent() on FocusEvent (@mrobinson, #44870)
in stop() on Window (@TimvdLippe, #44804)
in document.execCommand("delete") (@TimvdLippe, #44748)
in --debug-mozjs builds (@Gae24, @SharanRP, #44745, #45001)
when evaluating scripts in DevTools while paused (@atbrakhi, #45050)
when previewing some JS values in DevTools (@eerii, @atbrakhi, #45054)
when shaping zero-width spaces in layout (@mrobinson, #45176)
when toggling servoshell’s experimental mode at runtime (@mrobinson, @Loirooriol, #45226)

We’ve continued our long-running effort to use the Rust type system to make certain kinds of dynamic borrow failures impossible (@Gae24, @MavenRain, @Narfinger, @SteveSharonSam, @TimvdLippe, @elomscansio, @jdm, @kkoyung, @yezhizhen, #44712, #44759, #44879, #45014, #45058, #45061, #45076, #45098, #45110, #45149, #45117, #45184, #45201, #44806, #44930, #44942, #44946, #45233, #45181, #44659, #44660, #44664, #44668, #44992, #45000, #45081, #45009, #45225, #45087, #45244, #45245, #45247, #44663, #44665, #44993, #45040, #45053, #44647, #44671, #44681, #44717, #44733, #44686, #44653).

New contributors

A special thanks to the following people for landing their first patch in Servo:

AbdAlRahman Gad (@AbdAlRahmanGad, #45213)
Onyeka Obi (@MavenRain, #44806)
Steve Sharon Sam (@SteveSharonSam, #45030)
avis137 (@avis137, #44837)
Xabier Rodríguez (@calvaris, #45084)
June (@kimjune01, #44816)
Matt Van Horn (@mvanhorn, #44740)
nicole (@n0blenote, #44704)
panxt8 (@panxt8, #44991)

Interested in helping build a web browser? Take a look at our curated list of issues that are good for new contributors!

Donations

Thanks again for your generous support! We are now receiving 7659 USD/month (+4.2% from April) in recurring donations. This helps us cover the cost of our speedy CI and benchmarking servers, one of our latest Outreachy interns, and funding maintainer work that helps more people contribute to Servo.

Servo is also on thanks.dev, and already 35 GitHub users (+2 from April) that depend on Servo are sponsoring us there. If you use Servo libraries like url, html5ever, selectors, or cssparser, signing up for thanks.dev could be a good way for you (or your employer) to give back to the community.

7659 USD/month

10000

April in Servo: new Android UI, focus, forms, security fixes, and more!

2026-05-31T00:00:00Z

Servo 0.2.0 contains all of the changes we landed in April, which came out to yet another record 534 commits (March: 530). For security fixes, see § Security.

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