December in Servo: multiple windows, proxy support, better caching, and more!

Come along and meet us at FOSDEM 2026 – we’re speaking there too!

Posted 2026-01-23

Servo 0.0.4 and our December nightly builds now support multiple windows (@mrobinson, @mukilan, #40927, #41235, #41144)! This builds on features that landed in Servo’s embedding API last month. We’ve also landed support for several web platform features, both old and new:

Servo 0.0.4 showing new support for multiple windows

For better compatibility with older web content, we now support vendor-prefixed CSS properties like ‘-moz-transform’ (@mrobinson, #41350), as well as window.clientInformation (@Taym95, #41111).

We’ve continued shipping the SubtleCrypto API, with full support for ChaCha20-Poly1305, RSA-OAEP, RSA-PSS, and RSASSA-PKCS1-v1_5 (see below), plus importKey() for ML-KEM (@kkoyung, #41585) and several other improvements (@kkoyung, @PaulTreitel, @danilopedraza, #41180, #41395, #41428, #41442, #41472, #41544, #41563, #41587, #41039, #41292):

Algorithm
ChaCha20-Poly1305 (@kkoyung, #40978, #41003, #41030)
RSA-OAEP (@kkoyung, @TimvdLippe, @jdm, #41225, #41217, #41240, #41316)
RSA-PSS (@kkoyung, @jdm, #41157, #41225, #41240, #41287)
RSASSA-PKCS1-v1_5 (@kkoyung, @jdm, #41172, #41225, #41240, #41267)

When using servoshell on Windows, you can now see --help and log output, as long as servoshell was started in a console (@jschwe, #40961).

Servo diagnostics options are now accessible in servoshell via the SERVO_DIAGNOSTICS environment variable (@atbrakhi, #41013), in addition to the usual -Z / --debug= arguments.

Servo’s devtools now partially support the Network > Security tab (@jiang1997, #40567), allowing you to inspect some of the TLS details of your requests. We’ve also made it compatible with Firefox 145 (@eerii, #41087), and use fewer IPC resources (@mrobinson, #41161).

this website in Servo’s devtools, showing that the main request used TLS 1.3, TLS13_AES_256_GCM_SHA384 cipher suite, and X25519MLKEM768 key exchange, with HSTS enabled and HPKP disabled

We’ve fixed rendering bugs related to ‘float’, ‘order’, ‘max-width’, ‘max-height’, ‘:link’ selectors, <audio> layout, and getClientRects(), affecting intrinsic sizing (@Loirooriol, #41513), anonymous blocks (@Loirooriol, #41510), incremental layout (@Loirooriol, #40994), flex item sizing (@Loirooriol, #41291), selector matching (@andreubotella, #41478), replaced element layout (@Loirooriol, #41262), and empty fragments (@Loirooriol, #41477).

Servo now fires ‘toggle’ events on <dialog> (@lukewarlow, #40412). We’ve also improved the conformance of ‘wheel’ events (@mrobinson, #41182), ‘hashchange’ events (@Taym95, #41325), ‘dblclick’ events on <input> (@Taym95, #41319), ‘resize’ events on <video> (@tharkum, #40940), ‘seeked’ events on <video> and <audio> (@tharkum, #40981), and the ‘transform’ property in getComputedStyle() (@mrobinson, #41187).

Embedding API

Servo now has basic support for HTTP proxies (@Narfinger, #40941). You can set the proxy URL in the http_proxy (@Narfinger, #41209) or HTTP_PROXY (@treeshateorcs, @yezhizhen, #41268) environment variables, or via --pref network_http_proxy_uri.

We now use the system root certificates by default (@Narfinger, @mrobinson, #40935, #41179), on most platforms. If you don’t want to trust the system root certificates, you can instead continue to use Mozilla’s root certificates with --pref network_use_webpki_roots. As always, you can also add your own root certificates via Opts::certificate_path (--certificate-path=).

We have a new SiteDataManager API for managing localStorage, sessionStorage, and cookies (@janvarga, #41236, #41255, #41378, #41523, #41528), and a new NetworkManager API for managing the cache (@janvarga, @mrobinson, #41255, #41474, #41386). To clear the cache, call NetworkManager::clear_cache, and to list cache entries, call NetworkManager::cache_entries.

Simple dialogs – that is alert(), confirm(), and prompt() – are now exposed to embedders via a new SimpleDialog type in EmbedderControl (@mrobinson, @mukilan, #40982). This new interface is harder to misuse, and no longer requires boilerplate for embedders that wish to ignore simple dialogs.

Web console messages, including messages from the Console API, are now accessible via ServoDelegate::show_console_message and WebViewDelegate::show_console_message (@atbrakhi, #41351).

Servo, the main handle for controlling Servo, is now cloneable for sharing within the same thread (@mukilan, @mrobinson, #41010). To shut down Servo, simply drop the last Servo handle or let it go out of scope. Servo::start_shutting_down and Servo::deinit have been removed (@mukilan, @mrobinson, #41012).

Several interfaces have also been renamed:

Perf and stability

We can now evict entries from our HTTP cache (@Narfinger, @gterzian, @Taym95, #40613), rather than having it grow forever (or get cleared by an embedder). about:memory now tracks SVG-related memory usage (@d-kraus, #41481), and we’ve fixed memory leaks in <video> and <audio> (@tharkum, #41131).

Servo now does less work when matching selectors (@webbeef, #41368), when focus changes (@mrobinson, @Loirooriol, #40984), and when reflowing boxes whose size did not change (@Loirooriol, @mrobinson, #41160).

To allow for smaller binaries, gamepad support is now optional at build time (@WaterWhisperer, #41451).

We’ve fixed some undefined behaviour around garbage collection (@sagudev, @jdm, @gmorenz, #41546, mozjs#688, mozjs#689, mozjs#692). To better avoid other garbage-collection-related bugs (@sagudev, mozjs#647, mozjs#638), we’ve continued our work on defining (and migrating to) safer interfaces between Servo and the SpiderMonkey GC (@sagudev, #41519, #41536, #41537, #41520, #41564).

We’ve fixed a crash that occurs when <link rel=“shortcut icon”> has an empty ‘href’ attribute, which affected chiptune.com (@webbeef, #41056), and we’ve also fixed crashes in:

Donations

Thanks again for your generous support! We are now receiving 7110 USD/month (+10.5% over November) 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 30 GitHub users (+2 over November) 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. A big thanks from Servo to our newest Bronze Sponsors: Anthropy, Niclas Overby, and RxDB! If you’re interested in this kind of sponsorship, please contact us at [email protected].

7110 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.

Conference talks and blogs

We’ve recently published one talk and one blog post:

We also have two upcoming talks at FOSDEM 2026 in Brussels later this month:

Servo developers Martin Robinson (@mrobinson) and Delan Azabani (@delan) will also be attending FOSDEM 2026, so it would be a great time to come along and chat about Servo!

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