See what landed recently in Firefox Nightly!

Starting with Firefox 154, Firefox Nightly is testing a simpler tab context menu in Firefox Labs. It can be turned on in Settings > Firefox Labs > Streamline tab menu, and feedback is welcome on Mozilla Connect.

Fixed Firefox preventing Linux systems from going to sleep after a long browsing session.

Fixed arrow-key and Page Up/Down scrolling not working on some pages with embedded content from other sites.

Fixed characters from some less common scripts appearing as empty boxes on Windows.

Fixed text disappearing in Microsoft 365 Word Online and other web apps on Linux when typing with certain non-Latin keyboard layouts.

On Firefox for Android, autofill prompts now dismiss when focus moves away instead of remaining open until back navigation.

Firefox now opens mailto: links only in response to an explicit user action, so pages can no longer launch the default mail client unprompted.

Small PDFs can now be enlarged when printing by setting the scale above 100%, up to the full page size.

The Rules View now offers toggles to emulate the prefers-reduced-motion media feature. Also, emulation options have moved into a new panel behind the @ button.

The JSON Viewer now displays JSON Lines (JSONL/NDJSON) documents, including inline errors for invalid lines.

Starting with Firefox 154, Firefox Nightly now supports the alpha() CSS function. This is a relative color function that can be used to modify just the alpha component of a given color.

Starting with Firefox 153, Firefox Nightly ships an experimental implementation of the link-parameters property by Tyler Thrailkill.

Starting with Firefox 153, Firefox Nightly now supports two new keywords, closest-corner and farthest-corner, for the radial size in the circle() and ellipse() functions.

Starting with Firefox 154, Firefox Nightly now supports QUIC version 2 (RFC 9369) for HTTP/3 connections. Firefox offers both QUIC v1 and v2 using compatible version negotiation (RFC 9368). The server selects which version is used, so connections upgrade to QUIC v2 when the server chooses it and remain on QUIC v1 otherwise.

Firefox now supports the progress() CSS function. This is a math function that can be used in calculations to compute the position of a value relative to a start and an end.

SVG <a> elements now expose the same URL properties as HTML links, including protocol, host, pathname, and search.

Starting with Firefox 155, the RegExp Buffer Boundary proposal is now available for testing in Nightly builds by setting the javascript.options.experimental.regexp_buffer_boundaries preference.

The CSS Typed Object Model's StylePropertyMap now supports delete() for removing a property.

Starting with Firefox 155, Firefox Nightly offers limited support for the Speculation Rules API for same-origin prefetch, allowing pages to declare which links should be prefetched. This initial support covers only the immediate eagerness level and list source rules.

The CSS attr() function now supports values of any type, so authors can use attribute values in any property rather than only as strings in the content property.

Starting with Firefox 155, Nightly builds enable the Audio Session API, letting sites declare how their audio mixes with other applications.

Starting with Firefox 155, Nightly builds now support the at-rule() function for @supports. This allows authors to test for browser support of specific at-rules, such as @supports at-rule(@scope).