What’s New in Mozilla Firefox 153 ESR?

Mozilla has officially released the final builds for Firefox 153 Extended Support Release (ESR). Designed primarily for enterprise IT environments, organizations, and stability-focused users, this release provides a predictable, secure platform that will receive critical maintenance and security updates for the next 15 months.

Firefox 153 ESR builds upon the foundation of previous enterprise releases. It serves as the official successor to the Firefox 140 ESR branch, which continues receiving security patches until September 2026. Once the 140 series reaches its end-of-life, Firefox 153 ESR will maintain its position as a primary long-term release alongside the ongoing Firefox 115 ESR series.

---

Standout End-User & Interface Features

This release introduces several quality-of-life enhancements aimed at improving daily browsing workflows, media consumption, and security awareness:

• Quick Actions via Address Bar: You can now trigger utility tools directly from the address bar. Typing terms like pick color, color picker, or eyedropper allows you to select and copy hex codes from any webpage. Additionally, typing labs or experiment opens the Firefox Labs configuration menu directly.

• Integrated Container Isolation: Native support for containers allows you to segregate online tasks—such as work, personal, banking, or shopping—within a single browser window while keeping cookies and tracking scripts isolated.

• Enhanced PDF Capabilities: The built-in PDF viewer now supports document merging by dragging extra files directly into the sidebar. Users can also append images as standalone pages into existing PDF files.

• Active Location Alerts: Security indicators now actively signal site behavior. The location permission icon highlights in red whenever a website accesses real-time device location data.

• Tab Sharing via QR Codes: Firefox now allows you to generate a QR code for any open web page, enabling seamless tab handoff to mobile devices.

---

System Security & Platform Upgrades

Firefox 153 ESR implements stricter technical baselines to secure network requests and local file systems:

• Default Local Network Access Restrictions: To prevent unauthorized cross-origin requests into local network resources, strict Local Network Access restrictions are now enabled by default for all users.

• Extension File Isolation: Extensions are now restricted from accessing local system files by default, reducing potential attack surfaces.

• eIDAS Certificate Compliance: The browser now natively verifies and displays Qualified Website Authentication Certificates (QWACs) in full compliance with European eIDAS standards.

• Cookie Management Modernization: Outdated granular cookie settings under Settings > Privacy & Security have been streamlined into a unified Isolate cross-site cookies setting.

• Platform-Specific Media Optimizations: Windows users gain support for High Dynamic Range (HDR) video playback. Meanwhile, macOS users can utilize Apple’s system-wide Globe-F keyboard command for full-screen navigation, alongside better support for video overlays.

---

Developer-Focused Enhancements

Web developers gain new diagnostic options, testing environments, and expanded CSS and JavaScript specification support:

• Local Mode in Developer Tools: A new "Local Mode" panel allows developers to map local directories to custom origins. This simplifies testing for browser APIs that do not function over standard file:// protocols, eliminating the need to set up a local HTTP server.

• JavaScript Import Attributes: Developers can now use the text import attribute to import raw text files directly through the native ECMAScript module system.

• Error Stack Trace Limits: Support for the Error.stackTraceLimit property allows developers to explicitly set or query the maximum depth of captured JavaScript error stacks.

• CSS & HTML Spec Alignment: Includes partial support for ::-webkit-scrollbar pseudo-elements, the popover=hint specification, updated alignment-baseline keywords, and closest/farthest-corner keywords for circle() and ellipse() CSS functions. Standardized HTML parsing rules for <select> elements and the Intl.LocaleInfo interface have also been integrated.

• WebRTC Diagnostic Queries: Updated MediaCapabilities.decodingInfo() and .encodingInfo() methods now support a "webrtc" configuration parameter, enabling sites to test whether WebRTC audio/video streams will decode smoothly and efficiently.

---

Availability

The final binaries and source packages for 64-bit, 32-bit, and ARM64 systems are available for download directly from Mozilla’s distribution servers ahead of the official rollout.