Don't downgrade Firefox 63

Martin Brinkmann
Aug 6, 2018
Updated • Aug 6, 2018

Mozilla plans to change the backend for the storage.local API to indexedDB from JSON to improve performance in Firefox 63. The migration happens in the background and Firefox users who run Firefox 63 should not notice any issues afterward.

Problems may arise however if users downgrade Firefox to an earlier version or switch to a channel that is not yet at Firefox 63 or newer.

The change will land in Firefox Nightly first and if users load the Beta or Stable version of Firefox with the Nightly profile, they may run into data regression issues with extensions installed in the browser.

Mozilla revealed the change on the organization's Add-ons blog that it uses to inform developers of extensions for Firefox about upcoming changes and new features.

If your users switch between Firefox channels using the same profile during this time, they may experience data regression in the extensions they have previously installed.

Mozilla recommends that users don't downgrade from Firefox 63 in any form (be it by installing an older version and running it, or running an older version that is installed already using the same profile).

How to find out if the data has been migrated

firefox 63 downgrade

You can do the following to find out if the storage API has been migrated already to the new storage format:

  1. Load about:config?filter=extensions.webextensions.ExtensionStorageIDB.enabled in the address bar of the browser.
  2. Check the value of the preference.
    • True means that the data has been migrated.
    • False that Firefox uses the old format.
  3. Search for extensions.webextensions.ExtensionStorageIDB.migrated.
    1. If the Extension ID is set to true, the extension storage has been migrated.

What you can do to re-migrate the data

extensions migrated

Mozilla published instructions on re-migrating the extension data should it not be there after the migration. Note that it requires quite a few steps including removing the extension from Firefox and reinstalling it.

  1. Open about:debugging and write down the extension ID (or remember it).
  2. Open the profile folder of Firefox by loading about:profile and there the open folder option.
  3. Open the folder browser-extension-data.
  4. Open the Extension ID folder.
  5. Uninstall the extension.
  6. Copy the file storage.js.migrated which you find in the Extensions ID folder to a new file and name it storage.js.
  7. Open the browser console by selecting Menu > Web Developer > Browser Console or by using the shortcut Ctrl-Shift-J.
  8. Install the extension again.
  9. The browser console should display a migration message. Wait for this to happen.

Closing Words

If you need to run different Firefox channels, use different profiles (and you can even run the profiles simultaneously). You can copy profile data from one profile to the other to create copies if you want to work with the same data set.

Don't downgrade Firefox 63
Article Name
Don't downgrade Firefox 63
Mozilla plans to change the backend for the storage.local API to indexedDB from JSON to improve performance in Firefox 63.
Ghacks Technology News

Tutorials & Tips

Previous Post: «
Next Post: «


  1. Robert Ab said on August 7, 2018 at 6:38 pm
  2. Anonymous said on August 7, 2018 at 3:16 pm

    What does that means? They’ll replace .json with sqlite DBs?

    1. Martin Brinkmann said on August 7, 2018 at 4:35 pm

      At least in this case, yes.

  3. jan said on August 7, 2018 at 11:03 am

    Yes, one more thing to know and how to fix it in the postgraduate PhD program for advanced users. But the FF people do not want to know how close they are to the point of meltdown.

  4. AAA said on August 6, 2018 at 10:56 pm

    Mozilla is becoming more like Internet Explorer :(
    …today; I tried 32bit, 64bit, custom installation, automatic — but none could get sharp crispy Netflix quality that I could get via Edge.
    What did the fox say? 🙄

    1. Richard Allen said on August 7, 2018 at 7:08 pm

      I recently did a clean install of Win7 on my 9 year old laptop and gave it to my sister because she only has a work computer and often works from home.

      She just now told me Netflix is working fine for her and she’s using FF v61 x64. Laptop has a dual core processor, a GT 230M graphics card, 4GB of RAM with an inexpensive ADATA SSD hooked up to a 100+ Mbps connection. Nothing special.

      I think she was a little put out that I asked her to look. LoL. She normally watches Netflix on her ridiculously large Smart TV. Definitely a spoiled girl!

    2. Jonh said on August 7, 2018 at 8:32 am

      Same here sometimes. However one day I was browsing with Edge and one page didn’t work properly (weird issue considering its UA like Chrome), so I decided to open it with Firefox latest and it worked fantastic (showing tick boxes and web dialogs that didn’t appear with Edge). I remember one site that only worked for me with IE11, some months ago, so surprisingly.

    3. ZeoMal said on August 7, 2018 at 7:36 am

      If you look it up, that’s got nothing to do with Mozilla per se, as Netflix supports the highest quality (, only in Microsoft’s own browser.

  5. Richard Allen said on August 6, 2018 at 10:02 pm

    Thanks Martin, I wasn’t aware of that. I’ve been slacking about going to mozillaZine lately and haven’t checked the twitter feed lately. Shame on me.

  6. Satya Nadella Quote Generator said on August 6, 2018 at 7:59 pm

    Downgrade is for pussies

    1. TrackingCookieMonster said on August 8, 2018 at 11:40 am

      Keeping data in your browser is for pussies. Clean on exit gang.

    2. Richard Allen said on August 6, 2018 at 9:58 pm


  7. Anonymous said on August 6, 2018 at 7:55 pm

    There’s something odd going on with lately. I can’t open the “mobile” folders of , and For example, I can open as well as , but throws a 404 Not Found (or occasionlly a 504 Error).

    Is this only me?

    1. Richard Allen said on August 6, 2018 at 9:57 pm

      Same here.

      I’ve always used “” for browser updates on Android. If I didn’t want to wait. And I wouldn’t mention them if I didn’t feel they were trustworthy. Just saying.

Leave a Reply

Check the box to consent to your data being stored in line with the guidelines set out in our privacy policy

We love comments and welcome thoughtful and civilized discussion. Rudeness and personal attacks will not be tolerated. Please stay on-topic.
Please note that your comment may not appear immediately after you post it.