Firefox 153.0.0 Release Notes: JPEG XL & Settings Redesign

Firefox Nightly 153.0a1 hit the streets on May 19, 2026. This build packs a fresh batch of features and fixes for early testers. The firefox 153.0.0 release notes highlight a redesigned Settings page, support for JPEG XL images, and a new QR code sharing tool. It also adds support for Apple’s Globe-F full-screen shortcut. Developers get a new Error.stackTraceLimit property and popover=hint spec implementation. If you run Nightly, this update is ready to download.

This feature release targets Nightly channel users who want the latest browser innovations before they hit stable. The update introduces several user-facing changes, including a revamped Settings UI, new web platform support (JPEG XL, WebAssembly JS-Promise Integration), and improved PDF handling. Upgrade now to test these features and provide feedback to Mozilla.

What Changed

QR code sharing: Right-click any tab, select Share > Generate QR Code to create a QR for the open page. Also accessible via the address bar on macOS.
Apple full-screen shortcut: Added support for the Globe-F keyboard command to enter system-wide full-screen.
Firefox Labs quick action: Type “labs” or “experiment” in the address bar to open Firefox Labs instantly.
Settings redesign: Streamlined organization with clearer groupings and improved navigation.
PDF text selection: Selected text in PDFs now uses a clear highlight that respects OS high-contrast settings.
Share PDF as file (Android): Sharing a remote PDF now sends the file itself, not just its URL.
JPEG XL support: Nightly builds can now render the JPEG XL format, offering better compression than WebP, JPEG, PNG, and GIF.
WebAssembly JS-Promise Integration: Supports bridging JS Promises into WebAssembly modules for easier porting.
CSS attr() everywhere: The attr() function now works in any CSS property with custom parsing.
CSS baseline keywords: alignment-baseline accepts new values: alphabetic, ideographic, central, mathematical, hanging.
popover=hint spec: Implements the updated popover hint specification, removing inconsistent behaviors.
JavaScript Error.stackTraceLimit: Developers can set a max depth for error stack traces to optimize performance.
JavaScript Tracer in DevTools: Traces all JavaScript function calls (Nightly only, from Firefox 151).
HTML parsing for <select>: Updated rules to align with web standards for future customizable dropdowns.
In-memory JS compilation cache: Shared across same-domain navigation to speed up page loads (from Firefox 152).
AI feature controls (Android): New settings to enable fine-grained control and block future AI features (from Firefox 151).
Address bar autofill: Autofills pages you visit most, including specific in-site pages (from Firefox 152).

Why It Matters

User experience wins: The Settings redesign and QR code sharing cut steps for common tasks. PDF selection now looks consistent with other apps.
Web platform future: JPEG XL support sets Firefox apart for image quality and speed. The popover=hint spec improves interactive UI components.
Developer tools: Error.stackTraceLimit and the JavaScript Tracer give engineers more control over debugging and performance tuning.
Performance boost: The in-memory JS compilation cache reduces load times for returning visitors.

Who Should Upgrade

This release is particularly relevant for Nightly testers who want to evaluate new web platform features like JPEG XL, WebAssembly JS-Promise Integration, and the popover hint spec. Web developers and QA engineers should upgrade to test CSS attr() improvements and the new JavaScript tracing capability. Android users benefit from AI feature controls and improved PDF sharing. If you help shape Firefox’s future, grab this build now.

How to Upgrade

Open Firefox Nightly on your device.
Click the menu button (three horizontal lines) and select Help > About Firefox Nightly.
Firefox checks for updates automatically. If 153.0a1 is available, click “Restart to Update Firefox Nightly.”
For a manual download, visit the Firefox Nightly download page at firefox.com and choose your platform.

Usage Examples

Share a page with colleagues: Right-click a tab, choose Share > Generate QR Code. Display the QR code on a poster or monitor. Anyone scans it with their phone to open the page.
Quick access to experiments: Type “labs” in the address bar and select the Open Firefox Labs quick action. This lets you toggle experimental features in two seconds.
Optimize error stacks: In the DevTools console, set Error.stackTraceLimit = 50 before running performance-sensitive code to limit stack depth and reduce overhead.
Use JPEG XL images: Load a JPEG XL (.jxl) file in Nightly. Notice the same quality at roughly 20% smaller file size compared to JPEG.