Firefox 149.0: JPEG-XL on Rust and new APIs

Firefox 149.0: Rust JPEG-XL Decoder and Developer Improvements

Firefox 149.0 was released on March 24, 2026. Key changes include switching to the Rust-based JPEG-XL decoder jxl-rs instead of C++, faster PDF processing, HTTP/3 support in unstable networks, and default use of XDG Portal on Linux. The browser is available for Windows, Linux, and macOS.

Release Timeline Before 149.0

Firefox development followed the schedule: version 138 — April 2025, 139 — May 2025, 140 ESR — June 2025 with long-term support. Firefox 141 was released on July 22, 2025, 142 in August added LLM for extensions, 143 — September, 144 — October, 145 in November dropped 32-bit Linux support. December 2025 — 146, January 2026 — 147, February — 148 with the "AI Management" section.

Decoding and Rendering Technical Improvements

• JPEG-XL on Rust (jxl-rs): Replaces the C++ decoder, provides memory-safe processing. Similar to Chrome's approach after restoring format support.
• PDF processing: Faster, with image extraction from PDF via context menu.
• HTTP/3: Improved upload stability in unstable networks.
• XDG Portal on Linux: Default file picker, with GTK3 fallback.
• Linux error visuals: Updated UI elements.

WebRender layer compositor is enabled by default on Windows to reduce power consumption during fullscreen video and speed up WebGL/WebGPU.

New APIs for Web Developers

Added tools for mid/senior-level specialists:

• HTMLMediaElement.captureStream(): Matches the spec, supports :playing and :paused pseudo-classes, text elements with showPicker().
• Reporting API: Universal mechanism for web apps based on platform features.

These APIs simplify media and analytics integration without external libraries.

UI Features and Platform Changes

• Split View: Split screen for two pages in one tab. Activate via right-click on tab, supports tab groups.
• Share button: Add to toolbar via right-click on tab, integrates with Windows/macOS system sharing.
• Geolocation on Windows: Switches to modern Windows.Devices.Geolocation instead of Windows 7 API.

Security Enhancements

• Auto-blocking notifications and revoking permissions for SafeBrowsing sites.
• Stricter JS file loading in the parent process.

Changes target enterprise deployments and secure web app development.

Key Takeaways

• Switching JPEG-XL to Rust boosts memory safety without performance loss.
• New APIs expand media and reporting capabilities for web apps.
• Split View and sharing optimize UX without privacy trade-offs.
• WebRender compositor reduces GPU load in video/WebGL scenarios.
• Security hardened against malicious content and JS loads.

— Editorial Team