All versions since Firefox 157

Firefox 157

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.