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Firefox administrator reference

All versions since Firefox 143

All versions

Firefox 143

Released 16 September 2025.

These changes apply to Firefox 143 and Firefox ESR 140.3.0 unless explicitly stated.

Notes

  • Firefox ESR 128 goes out of support with this release. Firefox ESR 128 users are upgraded to Firefox ESR 140.

Firefox 144

Released 14 October 2025.

These changes apply to Firefox 144 and Firefox ESR 140.4.0 unless explicitly stated.

New in Firefox 144

  • GenerativeAI: Configure generative AI features. Chatbot is the only option that applies to the ESR.
  • VisualSearchEnabled: Enable or disable visual search. Does not apply to the ESR.

New in Firefox ESR 140.4.0

  • GenerativeAI: Configure generative AI features. Only the Chatbot option is available on the ESR.

Changes

  • Preferences: Allow setting the security.webauthn.always_allow_direct_attestation preference.

Fixes

  • Some print options were still shown when printing was disabled. (bug 1889569)
  • Windows Kerberos authentication with Extended Protection did not work with a SHA384 SSL certificate. (bug 1895277)

Notes

  • Firefox ESR 115 support for Windows 7/8 and macOS 10.12, 10.13 and 10.14 is extended to March 2026.

Firefox 145

Released 11 November 2025.

These changes apply to Firefox 145 and Firefox ESR 140.5.0 unless explicitly stated.

Mozilla has introduced Firefox Support for Organizations, a support offering for enterprise deployments of Firefox.

New in Firefox 145

  • LocalNetworkAccess: Configure local network access security features. Does not apply to the ESR.

Changes

  • GenerativeAI: Added an option to enable or disable all generative AI features.
  • EnableTrackingProtection: BaselineExceptions and ConvenienceExceptions can now be set in strict mode. Does not apply to the ESR.

Fixes

Firefox 146

Released 9 December 2025.

These changes apply to Firefox 146 and Firefox ESR 140.6.0 unless explicitly stated.

New in Firefox 146

  • BrowserDataBackup: Disable backup or restore of profile data. Does not apply to the ESR.

Changes

  • The version number, architecture and language were removed from the Windows uninstall registry key, improving compatibility with third-party tools. Does not apply to the ESR. (bug 1995769)
  • Firefox Labs can now be enabled regardless of the status of DisableTelemetry or DisableFirefoxStudies. Does not apply to the ESR. (bug 1972647)

Fixes

Firefox 147

Released 13 January 2026.

These changes apply to Firefox 147 and Firefox ESR 140.7.0 unless explicitly stated. Firefox ESR 140 is the current ESR, so enterprise changes are no longer backported to Firefox ESR 128.

Fixes

  • Private Window options were still available from the Firefox View tab when private browsing was disabled. (bug 2004669)
  • A performance regression affecting extension native messaging reached the ESR in Firefox ESR 140.7.0. In earlier Firefox 140-series builds, native messaging operations could experience significantly increased latency, affecting enterprise extensions that communicate with external processes. The release channel received this fix in Firefox 146. (bug 2002517)

Known issues

  • Using Trellix DLP Endpoint for Windows can cause crashes when dragging and dropping files. Set the security.sandbox.content.close-ksecdd-handle preference to false as a workaround.

Firefox 148

Released 24 February 2026.

These changes apply to Firefox 148 unless explicitly stated. Firefox ESR 140.8.0 shipped the same day, but these changes were not backported to it.

New in Firefox 148

Changes

  • GenerativeAI: Updated to cover PDF alt text generation and translations. (bug 2013938)
  • AI Controls settings now respect enterprise policy and locale or region restrictions. (bug 2005805)
  • Firefox now reports whether a profile is managed by enterprise policy, as policies.is_enterprise in the baseline telemetry ping. (bug 1997959)

Firefox 149

Released 24 March 2026.

These changes apply to Firefox 149 and Firefox ESR 140.9.0 unless explicitly stated.

New in Firefox 149.0.2

  • AIControls: Configure AI controls. Does not apply to the ESR.
  • IPProtectionAvailable: Prevent the built-in VPN from being available to users. Does not apply to the ESR.

Firefox 150

Released 21 April 2026.

These changes apply to Firefox 150 and Firefox ESR 140.10.0 unless explicitly stated. Firefox ESR 140 is the current ESR.

New in Firefox 150

  • RelaunchRequired: Require Firefox to be relaunched within a given period and notify the user of the upcoming relaunch. Does not apply to the ESR.
  • SitePolicies: Fine-grained control over policies for specific sites. Does not apply to the ESR.

Changes

Fixes

  • Homepage: The policy was not working correctly in Firefox 149. Fixed in Firefox 149.0.2. Does not apply to the ESR.

Notes

  • Firefox ESR 115 support for Windows 7/8 and macOS 10.12, 10.13 and 10.14 is extended to August 2026.

Firefox 151

Released 19 May 2026.

These changes apply to Firefox 151 and Firefox ESR 140.11.0 unless explicitly stated. Firefox ESR 140 is the current ESR, and enterprise changes are no longer backported to Firefox ESR 128.

Firefox 153 will be the next ESR. As that transition approaches, fewer non-security fixes and policy changes will be backported to Firefox ESR 140. If you use the ESR, we recommend testing with Firefox Beta or Nightly to identify issues before Firefox ESR 153 ships.

New in Firefox 151

  • DefaultSerialGuardSetting: Control use of the Web Serial API. Does not apply to the ESR.
  • XSLTEnabled: Enable or disable support for the XSLTProcessor JavaScript API and the XSLT processing instruction. Does not apply to the ESR.

Changes

Fixes

  • DisableRemoteImprovements: The policy was not reflected correctly in preferences. Firefox 151 only.
  • Sites blocked by enterprise policy did not display the correct error message. Firefox 151 only.

Firefox 152

Released 16 June 2026.

These changes apply to Firefox 152 unless explicitly stated. Firefox ESR 140.12.0 shipped the same day, but most of these changes were not backported to it.

Changes

  • DefaultSerialGuardSetting: Web Serial support is now disabled by default when Firefox is managed by enterprise policies.
  • ExtensionSettings: Force-installed extensions are now always updated automatically, regardless of the updates_disabled setting. (bug 2037243)
  • FirefoxHome: Allow configuration of the Weather experience. Also in Firefox ESR 140.12.0.
  • ManagedBookmarks: Allow specifying favicons directly for managed bookmarks.
  • Chatbot content is now available to extensions from content scripts. (bug 1980404)
  • Firefox now accepts TURN server responses whose XOR-MAPPED-ADDRESS does not match the ICE check, improving compatibility with some TURN server implementations. (bug 2034159)

Fixes

Firefox 153

Released 21 July 2026.

These changes apply to Firefox 153 and Firefox ESR 153 unless explicitly stated. Firefox ESR 153 is the new ESR - enterprise changes are no longer backported to Firefox ESR 140. Policies listed under Firefox ESR 153.0.0 became available to ESR admins for the first time in this release.

New in Firefox 153

Changes

  • Containers: Updated for the new container color palette. Existing color names are migrated to the new names automatically.
  • Cookies: Behavior and BehaviorPrivateBrowsing accept partition-foreign, the new name for the reject-tracker-and-partition-foreign cookie behavior. Configurations using the old name continue to work.
  • ExtensionSettings: Control extension host permissions using runtime_allowed_hosts and runtime_blocked_hosts, and control which permissions extensions may request using allowed_permissions.
  • Users can no longer change the host permissions of Manifest V3 extensions installed using force_installed.
  • ExtensionSettings: force_installed and normal_installed extensions can be installed directly from addons.mozilla.org when install_url is omitted.
  • Homepage: Added a NewTabOnRestore option to open the default start page or about:newtab after restoring a previous session.
  • ManagedBookmarks: Bookmarklets using javascript: URLs are now supported.
  • Automatically discovered printers are now listed after manually configured printers in the print destination list. (bug 1996569)
  • Firefox installed from a macOS .pkg package can now update without prompting for administrator credentials. (bug 1812480)

Fixes

New in Firefox ESR 153.0.0

Firefox 154

Released 18 August 2026.

These changes apply to Firefox 154 and Firefox ESR 153.1.0 unless explicitly stated. Firefox ESR 153 is the current ESR.

Firefox moves from a four-week to a two-week release cycle beginning with Firefox 155. Bug fixes, updates and features reach users more quickly once they are ready to ship.

New in Firefox 154

Changes

  • SanitizeOnShutdown: Added an Exceptions option to configure sites whose data should not be cleared on shutdown. Firefox 154 only. (bug 2049937)

Fixes

  • SearchEngines: PreventInstalls did not prevent users from manually adding search engines in Settings or from the context menu. (bug 2052965)
  • The -width and -height command-line options did not correctly set the Firefox window size. Firefox 154 only. (bug 1635927)
  • Extended Protection (channel and service binding) for Windows SSPI authentication worked when using SPNEGO but not when using Kerberos directly. (bug 1179722)

Firefox 155 Latest

Released 1 September 2026.

These changes apply to Firefox 155 and Firefox ESR 153.2.0 unless explicitly stated. Firefox ESR 153 is the current ESR.

New in Firefox 155

  • DisableLaunchOnLogin: This policy prevents Firefox from launching automatically when the user logs in (Windows only in 155). Does not apply to the ESR. (bug 2001734)

Changes

  • SitePolicies: Added an HttpsOnly option to prevent specific sites from being loaded over HTTP. Firefox 155 only. (bug 2045980)
  • Captive portal and network connectivity checks now use firefox-portal-detection.com instead of detectportal.firefox.com. Network allowlists and proxy rules naming the old domain need updating. Firefox 155 only. (bug 2049252, bug 1898891)

Fixes

  • ExtensionSettings: In Firefox 154 and Firefox ESR 153.1.0, configurations that quoted booleans ("true") would break and an invalid entry discarded the whole policy. The validator is relaxed to accept quoted booleans again, and invalid entries are now individually skipped. (bug 2065965)
  • SearchEngines: Contextual search prompted users to install a search engine when PreventInstalls was true. Firefox 155 only. (bug 2055614)
  • Locking legacy preferences such as pref.general.disable_button.default_browser didn't disable the corresponding controls in Firefox Settings, following the Settings rewrite. (bug 2056928, bug 2055887)
  • Firefox reported that it could pin itself to the taskbar when Windows Group Policy blocked pinning. Firefox 155 only. (bug 2059920)