According to Mozilla’s release notes, Mozilla has released Firefox 153 Extended Support Release (ESR), which was first made available to ESR channel users on July 21, 2026.
This update includes all the changes since Firefox 140 ESR, such as a new profile management system, Split View, enhanced fingerprinting 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 are automatically upgraded to Firefox 153 ESR.
Mozilla recommends that enterprise administrators test Firefox 153 ESR with their current configuration, extensions, authentication systems, and deployment tools before the automatic upgrade.
Profile management, split view, on-device AI features, and enterprise controls
Firefox 153 ESR introduces a profile management system that separates browsing into separate 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 webpages simultaneously in the same window, open links directly in Split View, rearrange pages, and search open tabs. The address bar now includes quick actions like unit and time zone conversion, muting all browser audio, and displays search results as the user types. Firefox also supports copying links from 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 says these features process data locally where possible to protect user privacy.
In a managed environment, enterprise administrators can centrally manage Firefox’s Generator AI features through enterprise policy. This allows administrators to disable or restrict AI features in deployment rather than leaving the choice up to individual users.
Security, privacy, and platform-specific changes
Firefox 153 extends ESR security protections. Fingerprinting protection is now widespread in both standard and strict advanced tracking protection modes, making it more difficult for sites to uniquely identify users.
Advanced Tracking Protection also adds stronger safeguards against bounce tracking and prevents websites from accessing local network resources without user permission.
Phishing and malware protection now uses Safe Browsing V5, and the Firefox Password Manager uses AES-256 encryption to protect stored logins. Private browsing now allows users to immediately end a session and temporarily relax tracker blocking for individual sites when necessary for compatibility.
Many updates are specific to each operating system.
On Windows, Firefox now supports installing websites as standalone web apps pinned to the taskbar. Web apps are available through Microsoft Store installation, and geolocation requests now integrate more effectively with Windows location permissions.
On macOS, Firefox now uses a dedicated GPU process by default, allowing graphics failures to be fixed without restarting the browser. WebGPU is also enabled by default on Apple Silicon Macs.
On Linux, Firefox supports native fractional scaling on Wayland, no longer requires a restart after package manager updates, uses less memory, supports XDG Base Directory Specification, and now provides RPM packages for Red Hat, Fedora, openSUSE, and other RPM-based distributions.
Steps for administrators preparing for upgrades, web platform updates, and availability
Enterprise administrators managing Firefox ESR deployments should test new releases before the automatic upgrade from Firefox 140 ESR is implemented:
- Deploy Firefox 153 ESR in a test environment and validate existing enterprise policies as AI features and other defaults change.
- Verify that extensions, authentication systems, and native messaging integration work as expected. Mozilla notes that a native messaging performance regression was fixed in this release.
- Review Generative AI policy controls and determine whether to disable or restrict AI features throughout the deployment.
- Updated references to the Enterprise Policy documentation, now located at firefox-admin-docs.mozilla.org.
- If necessary, apply an AppUpdatePin policy to prevent upgrades on specific machines during testing.
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 adds support for the ESR View Transition API, expands WebGPU support to Windows and Apple Silicon Macs, and introduces several modern web platform APIs, including the Navigation API, URLPatterns, Trusted Types, Sanitizer API, and prioritized task scheduling.
Mozilla has not announced the exact date when Firefox 140 ESR users will automatically upgrade to Firefox 153 ESR. Firefox 140 ESR will continue to receive security updates until the transition is complete.
Administrators who need to delay upgrades can pin updates, but Firefox 140 ESR will eventually reach end of support, after which security updates will stop.
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