Mozilla has released Firefox 153 Extended Support Release (ESR), first available to ESR channel users on July 21, 2026, according to Mozilla’s release notes.
This update includes all the changes since Firefox 140 ESR, such as a new profile management system, split view, improved fingerprint protection, AES-256 password encryption, and on-device AI features. Firefox 140 ESR will continue to receive security updates during the transition period until users automatically update to Firefox 153 ESR.
Mozilla recommends that enterprise administrators test Firefox 153 ESR with their current configurations, extensions, authentication systems, and deployment tools before automatically updating.
Profile management, split view, on-device AI features, and enterprise controls
Firefox 153 ESR introduces a profile management system that separates browsing into different profiles, each with its own name, avatar, and color theme. Tabs, bookmarks, passwords, and browsing history remain separate for each profile. The release also adds built-in profile backup and restore to support device migration or data recovery.
Split View allows users to view two web pages side by side in a single window, open links directly in Split View, rearrange pages, and search for open tabs. The address bar now includes unit and time zone conversion, quick actions like muting all browser audio, and displays search results as the user types. Firefox also supports copying links to highlighted text, and the Settings interface has been reorganized.
Firefox 153 ESR introduces several AI-powered features, including on-device tab organization, AI-assisted link previews, integrated AI search, and centralized controls for managing AI features. Mozilla states that these features process data locally whenever possible to protect user privacy.
In managed environments, enterprise administrators can centrally manage Firefox’s generative AI features through enterprise policy. This allows administrators to disable or restrict AI features across deployments rather than leaving the choice up to individual users.
Security, privacy, and platform-specific changes
Firefox 153 ESR expands security protections. Fingerprint protection is now broader in standard and strict enhanced tracking protection modes, making it more difficult for sites to uniquely identify users.
Improved tracking protection also adds stronger protections against bounce tracking and restricts websites from accessing local network resources without user permission.
Phishing and malware protection now uses Safe Browsing V5, and Firefox Password Manager uses AES-256 encryption to protect stored logins. Private browsing now allows users to instantly end a session and temporarily relax tracker blocking for individual sites when necessary for compatibility reasons.
Several updates are specific to each operating system.
On Windows, Firefox now supports installing websites as standalone web applications pinned to the taskbar. Web apps are available through Microsoft Store installs, and geolocation requests now integrate more effectively with Windows location permissions.
On macOS, Firefox now uses a dedicated GPU process by default, allowing you to recover from graphics crashes without restarting the browser. WebGPU is also enabled by default on Apple Silicon Macs.
On Linux, Firefox supports native fractional scaling in Wayland, no longer requires reboots after package manager updates, uses less memory, supports the XDG base directory specification, and now provides RPM packages for Red Hat, Fedora, openSUSE, and other RPM-based distributions.
Steps for administrators preparing for the upgrade, web platform updates, and availability
Enterprise administrators managing Firefox ESR deployments should test the new version before the Firefox 140 ESR automatic update is applied:
- Deploy Firefox 153 ESR in a test environment and validate existing business policies as AI features and other defaults have changed.
- Confirm that extensions, authentication systems, and native messaging integrations are working as expected. Mozilla notes that a native messaging performance regression was fixed in this release.
- Review your generative AI policy controls and determine whether to disable or restrict AI features across your entire deployment.
- Update references to the enterprise policy documentation, now located at firefox-admin-docs.mozilla.org.
- Apply the AppUpdatePin policy to delay updates on specific machines during testing, if necessary.
Testing during the transition window allows administrators to identify and report issues before users automatically upgrade from Firefox 140 ESR to Firefox 153 ESR.
Firefox 153 ESR adds support for the View Transitions API, extends WebGPU support to Windows and Apple Silicon Macs, and introduces several modern web platform APIs, including the Navigation API, URLPattern, Trusted Types, Sanitizer API, and Prioritized Task Scheduling.
Mozilla has not announced the exact date when Firefox 140 ESR users will be automatically upgraded to Firefox 153 ESR. Firefox 140 ESR will continue to receive security updates until the transition is complete.
Administrators who need to delay the update can pin the update, but Firefox 140 ESR will eventually reach the end of support, after which security updates will stop.
