If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort?
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs For JS `fetch()` interop, in 2026 it would be nice to get proper `user-agent` header control.
It has been an allowed/customizable header according to specs since 2015, but (to the best of my knowledge) it still doesn't work on some browsers (for reference, Firefox already supports this).
It already has a WPT test: https://github.com/web-platform-tests/wpt/pull/39301 -
If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
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@firefoxwebdevs File System Access API. I'd be fine if you carved out `showDirectoryPicker()`, or put it behind a scary permission prompt. It enables so many powerful editor-like apps, from Photoshop to VS Code.
@tomayac @firefoxwebdevs 100% this. Used by a vast majority of Construct users to save their work when available, and so a big reason to use our PWA in Chrome rather than Firefox
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs CSS Grid Lanes
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@firefoxwebdevs File System Access API. I'd be fine if you carved out `showDirectoryPicker()`, or put it behind a scary permission prompt. It enables so many powerful editor-like apps, from Photoshop to VS Code.
@tomayac @firefoxwebdevs Definitely! File System Access allows web apps to avoid relying on online accounts (you can save and load files without the fs apis, but the experience is subpar)
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs WebGPU
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs "corner-shape" support
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs WebAuthn still doesn't work correctly for multi-device passkeys, WebUSB not being supported makes many useful applications not usable on Firefox.
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
MathML
Mathematics Rendering · Issue #1140 · web-platform-tests/interop
Description This proposal seeks to improve the success rate of the already defined MathML presentation tests https://wpt.fyi/results/mathml/presentation-markup?label=experimental&label=master&aligned (Resubmission of #787) as the problem...
GitHub (github.com)
.... because shipping 1.1MB of JavaScript on Wikipedia articles is a tough compromise.
T414055 Performance review of MathJax client-side mode
>>! @Krinkle wrote at T271001#11499253:
Phabricator (phabricator.wikimedia.org)
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MathML
Mathematics Rendering · Issue #1140 · web-platform-tests/interop
Description This proposal seeks to improve the success rate of the already defined MathML presentation tests https://wpt.fyi/results/mathml/presentation-markup?label=experimental&label=master&aligned (Resubmission of #787) as the problem...
GitHub (github.com)
.... because shipping 1.1MB of JavaScript on Wikipedia articles is a tough compromise.
T414055 Performance review of MathJax client-side mode
>>! @Krinkle wrote at T271001#11499253:
Phabricator (phabricator.wikimedia.org)
@krinkle which bits are missing in the latest versions of browsers?
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs VirtualKeyboard API:
VirtualKeyboard API - Web APIs | MDN
The VirtualKeyboard API provides developers control over the layout of their applications when the on-screen virtual keyboard appears and disappears on devices such as tablets, mobile phones, or other devices where a hardware keyboard may not be available.
MDN Web Docs (developer.mozilla.org)
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs
Reference target for cross root aria, or something like it
Declarative custom elements
DOM Parts and Template instantiation -
@ausi just to double check, you mean margin-trim, not text-box-trim?
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@gundersen would you be ok if it was behind a site permission addon? https://support.mozilla.org/en-US/kb/site-permission-add-ons
@firefoxwebdevs Yes, as long as there is a good way to detect a blocked permission, so you can reask the user or gracefully degrade the experience.
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs
inline if() CSS -
@ausi just to double check, you mean margin-trim, not text-box-trim?
@firefoxwebdevs yes, margin-trim. Safari supports it and I think Chrome is working on it too IIRC.
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs Missing CSS random() has previously blocked me from porting JS to CSS.
types: `random()` | Can I use... Support tables for HTML5, CSS3, etc
"Can I use" provides up-to-date browser support tables for support of front-end web technologies on desktop and mobile web browsers.
(caniuse.com)
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If you had to pick _one_, which web platform feature would you like in Firefox that isn't part of the Interop 2026 effort? https://hacks.mozilla.org/2026/02/launching-interop-2026/#new-features
@firefoxwebdevs The new "install app" button in Firefox for Windows is a welcome addition, but makes it hard to provide good user guides, as support is not guaranteed. I hope you are working on expanding support to all platforms.
An alternate way to make this easier, is to suppprt the install button, which would make guides much simpler and no longer dependent on specific browser knowledge.
MSEdgeExplainers/WebInstall/explainer-current-doc.md at main · MicrosoftEdge/MSEdgeExplainers
Home for explainer documents originated by the Microsoft Edge team - MSEdgeExplainers/WebInstall/explainer-current-doc.md at main · MicrosoftEdge/MSEdgeExplainers
GitHub (github.com)
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@krinkle which bits are missing in the latest versions of browsers?
WPT cover a dozen or so missing bits.
Beyond that, the clearest cut ones are cataloged and polyfilled at https://github.com/w3c/mathml-polyfills. Compare https://w3c.github.io/mathml-polyfills/acid-test.html in two tabs with and without the transform applied.
For things that are implemented but have known bugs, there is for example a layout bug with mathrm introducing whitespace in Firefox between symbols, where Chrome/Safari/MathJax don't:
