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Firefox Release Notes

Release Notes tell you what’s new in Firefox. As always, we welcome your feedback. You can also file a bug in Bugzilla or see the system requirements of this release.

56.0 Firefox Release

September 28, 2017

Version 56.0, first offered to Release channel users on September 28, 2017

Today's release gives Firefox users a better experience with features like Firefox Screenshots, Send Tabs, and more control over the browser with an improved (and searchable) preferences section. It also includes incremental performance improvements that move us closer to our biggest release of the year, coming in November.

We'd like to extend a special thank you to all of the new Mozillians who contributed to this release of Firefox!


  • Launched Firefox Screenshots, a feature that lets users take, save, and share screenshots without leaving the browser

  • Added support for address form autofill (en-US only)

  • Updated Preferences

    • Added search tool so users can find a specific setting quickly
    • Reorganized preferences so users can more easily scan settings
    • Rewrote descriptions so users can better understand choices and how they affect browsing
    • Revised data collection choices so they align with updated Privacy Notice and data collection strategy
  • Media opened in a background tab will not play until the tab is selected

  • Improved Send Tabs feature of Sync for iOS and Android, and Send Tabs can be discovered even by users without a Firefox Account



  • Replaced character encoding converters with a new Encoding Standard-compliant implementation written in Rust

  • Added hardware acceleration for AES-GCM

  • Updated the Safe Browsing protocol to version 4

  • Reduced update download file size by approximately 20 percent

  • Improved security for verifying update downloads



  • Startup crash with RelevantKnowledge adware installed. Firefox Support has helpful instructions to remove it. (bug 1394550)

  • Startup crashes with 64-bit Firefox on Windows 7, for users of Lenovo's "OneKey Theater" software for IdeaPad laptops. To fix this crash, please re-install 32-bit Firefox. (bug 1369361)

  • Users running Firefox for Windows over a Remote Desktop Connection (RDP) may find that audio playback is disabled due to increased security restrictions. Learn how to mitigate this issue until it is corrected in an upcoming release.

  • Due to a bug in Mac OS X High Sierra, fullscreen mode has some issues (bug 1390125)

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