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Extensions in Firefox 70

Welcome to another round of new additions and changes to extensions, this time in Firefox 70. We have a new API, some improvements on existing APIs, and some great additions to Firefox Developer Tools to make it easier to debug your extensions.

Network Status

Firefox 70 features a new network status API. [Edit: It turns out this is not a public API as we determine the best way forward. If we can do this via web standards instead, that would likely be more useful!]

Downloads API Improvements

We’ve made a few improvements to the downloads API in Firefox 70. By popular request, the Referer header is now allowed in the API’s headers object. This allows extensions, such as download managers, to download files for sites that require a referrer to be set.

Also, we’ve improved error reporting for failed downloads. In addition to previously reported failures, the API will now report an error in case of various http 4xx failures. This makes the API more compatible with Chrome and gives developers a way to react to these errors in their code. [Edit: Sorry if I got your hopes up! This is actually coming in Firefox 71!]

Privacy API Improvements

If you are using the API and are modifying webRTCIPHandlingPolicy, we’ve made some compatibility changes to the disable_non_proxied_udp setting. This setting now better matches Chrome’s behavior. If your add-on relied on the Firefox-specific behavior, you can make use of the new setting proxy_only.

Extension Storage Inspector

Starting in Firefox 70, Firefox finally supports inspecting data from the API using the Devtools Storage Inspector. When you inspect an add-on via about:debugging, you will find a new Extension Storage section in the storage panel. While changing the values is not currently supported, this will make debugging your add-ons even easier.

Firefox developer tools showing extension storage data in a multi-column list.

Extension Storage Inspector

Unsupported Theme Properties

The accentcolor, headerURL and text_color properties are now unsupported. Please make use of the replacement properties frame, theme_frame, and tab_background_text. You can find more information on our previous deprecation announcement.


  • When managing extension shortcuts, you will now be notified if a shortcut is already in use.
  • The browser.notifications.onClicked and browser.notifications.onShown event callbacks are no longer called with a superfluous second parameter.
  • Logging has been improved when the native messaging host manifest is missing.
  • Various performance improvements, making startup quicker for Firefox users with add-ons.

Special thanks this time goes to our volunteers Trishul Goel, Myeongjun Go, Graham McKnight and Tom Schuster. We’ve also received an awesome contribution from Mandy Cheang as part of her internship at Mozilla. Keep up the great work everyone!

8 comments on “Extensions in Firefox 70”

  1. Tim wrote on

    I am finding that the debugger no longer works at all in the new inspect tab. It stops on a breakpoint but I am unable to step at all, using the step over, and it never continues.

  2. Juraj Mäsiar wrote on

    Could you provide MDN link for the “browser.networkStatus” API?
    Or estimate when it’s gonna be made?

  3. raccoon wrote on

    first of all, update this site.

    secondly, get parity with the old add-on system, PLEASE!

    thirdly, please bring back the cookie controls for extensions like EditThisCookie

  4. Is this the reason ALL extensions are brokeken afer the update to Firefox 70? wrote on

    They did it again, it seems. Not a single extension worked on my Firefaox after the update to version 70. Well done…

    1. Caitlin Neiman wrote on

      Sorry to hear that! You might want to visit for help.

  5. MusicLover67 wrote on

    How can I roll back to Firefox 69 until this is fixed? Firefox 70 won’t run with ANY extensions installed.

    1. Caitlin Neiman wrote on

      Yikes, that doesn’t sound right. You might want to visit to get this sorted.

      1. Robin wrote on

        Why NOT let us roll back. It might be okay for the complete geeks who can debug in Linux but when a new release does NOT work for a general user a simple solution is required. I have spent too much time looping through ‘support’ pages and just want to go back to something that worked for me – don’t care about all the new stuff. Give me back my video streaming so I can watch live and catch-up TV on my PC!!!
        At least I have found Chromium is working – which is now my default browser.