All versions since Firefox 155

Firefox 155

September 1, 2026

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

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)

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)

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)

Some sites may load slowly or fail to load on networks that block UDP. This can affect corporate networks where a proxy or firewall blocks QUIC as part of TLS inspection. To work around it, set network.http.happy_eyeballs_enabled to false with the Preferences policy. A fix is planned for the next dot release. Does not apply to the ESR. (bug 2063452)

September 15, 2026

These changes apply to Firefox 156 and Firefox ESR 153.3.0 unless explicitly stated. Firefox ESR 153 is the current ESR.

FirefoxHome: Added a Widgets option to turn the new tab widgets on or off with Enabled, and to block individual widgets by ID with Blocked. (bug 1980406)
SitePolicies: Added a DisableServiceWorkers option to stop specific sites from registering or using service workers. Firefox 156 only. (bug 2045811)
DisableLaunchOnLogin: Now applies on macOS as well as Windows, following the macOS launch on login implementation. Does not apply to the ESR. (bug 2053447)

DefaultBrowserSettingEnabled: Firefox startup and in-product set-as-default actions did not honor the default browser policies. (bug 2065138)
Cookies: Page Info did not consistently disable cookie permission controls that were set by policy, for both a locked cookie behavior and the Block list. (bug 2061452)
DisablePrivateBrowsing: The "New Private Window" item was still shown in the menubar File menu. (bug 2063975)
InstallAddonsPermission: The "Discover extensions" button in the extensions panel was not hidden when installs were blocked. Firefox 156 only. (bug 2041238)
FirefoxHome: Controls in the new tab customize panel are now disabled when the corresponding preference is locked. Firefox 156 only. (bug 1983258)

September 29, 2026

These changes apply to Firefox 157 and Firefox ESR 153.4.0 unless explicitly stated. Firefox ESR 153 is the current ESR.

AIControls: Added a SpeechRecognition option to make on-device speech recognition available or block it, with Locked to prevent users from changing it. Firefox 157 only. (bug 1940906)
about:policies now shows an error for a policy that only partially applied, naming the entry that failed, instead of listing it as active. (bug 2067123)

Homepage: In Firefox 154 and Firefox ESR 153.1.0, setting URL to several homepages separated by | stopped working after policy validation changes. The pipe separator is accepted again, and the extra URLs are treated as Additional. (bug 2067248)
Handlers: An invalid mimeTypes entry caused every later entry, including the extensions and schemes blocks, to be discarded. Invalid entries are now skipped individually. (bug 2067099)

Firefox ESR 140 goes out of support with this release. Firefox ESR 140.17.0 is its final build.

October 13, 2026

Upcoming, not yet released.

These changes apply to Firefox 158 and Firefox ESR 153.5.0 unless explicitly stated. Firefox ESR 153 is the current ESR.

ClearOnShutdown: Clear browsing data when the browser closes. Supersedes SanitizeOnShutdown, which is ignored when both are set. (bug 2040977)

ClearOnShutdown: Clear browsing data when the browser closes. Supersedes SanitizeOnShutdown, which is ignored when both are set. (bug 2040977)

SitePolicies: Added a Container option to load matching sites in a dedicated container, with ephemeral to clear its data after the last tab closes and at shutdown. Firefox 158 only. (bug 2045801, bug 2045798)
ContentAnalysis: Added InterceptionPoints.ClipboardCopy to send data copied from web content to the DLP agent. Off by default, so existing deployments are unaffected. Firefox 158 only. (bug 2067877)
ExtensionSettings: An entry with update_url but no install_url now installs the add-on from the update manifest, so self-hosted add-ons no longer need an install_url. Firefox 158 only. (bug 2061439)
DisableDeveloperTools: Now also disables Marionette and the Remote Agent, so browser automation tools that rely on them no longer work while the policy is set.
Extensions: Add-ons listed in Uninstall are now removed at every startup, not only when the policy changes.
The illustration on network error pages can be hidden by setting browser.netError.illustration.enabled to false. Administrators may want to set this using the Preferences policy. Firefox 158 only. (bug 2061552)

Policy URL fields rejected some valid URLs, such as internationalized domain names, non-ASCII paths and URLs containing spaces. (bug 2067819)
SanitizeOnShutdown: When the policy turned clearing on, Manage Exceptions and the category settings in Firefox Settings were disabled too, even for categories the policy left unset. Firefox 158 only. (bug 2065295)
DisableFirefoxAccounts: The toolbar could report a signed-in account when accounts were disabled. Firefox 158 only. (bug 2066062)
The Labs quick action in the address bar was still shown when Firefox Labs was turned off with UserMessaging, and Manage AI was still shown when browser.preferences.aiControls was false. Firefox 158 only. (bug 2070378)
WebsiteFilter: Blocking is now applied more consistently to redirected and embedded content.
Site lists in policies such as Permissions and PopupBlocking now also apply when a host is written with a trailing dot, such as example.com..
A policy set to null could stop other policies from applying.
The toolkit.policies.perUserDir preference is now only adhered to in automated testing.

Firefox ESR 140 is no longer supported. Firefox ESR 140.17.0, released with Firefox 157, was its final build.