Mozilla improves the reliability of Firefox's Sync service

Martin Brinkmann
Sep 19, 2020

Firefox users may use built-in sync functionality to synchronize data between instances of Firefox. These instances can be on the same computer, e.g. different profiles, or on different local or remote machines.

Syncing is useful to make sure that certain data, say bookmarks and passwords, are always identical between devices that you use.

firefox sync new backend

One of the main issues with Firefox's sync service was that it was not designed to be a backup service. While it did support syncing data to the cloud to push the data to other devices, it happened at times that the service would lose some of the data.

Mozilla started to work on a new Rust-based sync service for Firefox and has revealed it now in a new blog post on the official Services blog.

One of the core differences between the old and new Sync backend is that the new one behaves like a backup service now; this means that it won't lose databases or data anymore as it relies on a distributed database to store the data secure.

A lot of folks expected it to be a Backup service. The good news is, now it is a backup service. Sync is more reliable now. We use a distributed database to store your data securely, so we no longer lose databases (or your data echos).

Mozilla's Support site lists quite a few cases of lost data, e.g. of users who formatted their PC, reinstalled Firefox, enabled Sync, only to find out that Sync was not finding any data.

A typical answer that users received for the issue they experienced is published below:

Firefox Sync is NOT A BACKUP SERVICE. It was not designed to be one, nor does it function like one. There's not necessarily a permanent or complete copy of your data on the Firefox Sync server.

Additionally, some account actions (like changing password) cause the Firefox Sync data to be erased.

The data is stored using Google Cloud's Spanner database, and the new backend is compatible with old and new versions of Firefox that support sync, and self-hosting as well. Users who self-host the Sync server need some patience though as Mozilla is still working on getting rid of bugs and other issues. Adventurous users can help Mozilla by providing feedback after setting up a self-hosted solution.

Additional information is available on the Syncstorage RS repo on GitHub.

Closing Words

The quintessence is that Firefox's Sync service will be more reliable in the future, and that the days of sync data not being available anymore are finally over once the migration completes.

Now You: Do you use Firefox Sync?

Mozilla improves the reliability of Firefox's Sync service
Article Name
Mozilla improves the reliability of Firefox's Sync service
Mozilla announced in September 2020 that it has modernized the Sync infrastructure that its Firefox web browser uses to eliminate data loss issues.
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  1. Alex said on September 20, 2020 at 5:17 am

    Dear Mozilla,
    I have no “privilege” or whatever it is called. I was born into a poor family and had to work my way up. I learned how it is like to be screwed over, humiliated, bullied by others even though I was white.

    I am switching to Brave. Brave on Linux.

    P.S. Don’t piss honest people off! We are capable of more than you think.
    Former Mozilla user

    1. ATC said on September 20, 2020 at 9:12 am

      Wow. Just wow. Trumpers take over Ghacks.

      1. Anonymous said on September 21, 2020 at 9:51 am

        lmao imagine being this delusional an seeing Trump in any comment you don’t like.

      2. Iron Heart said on September 21, 2020 at 12:34 pm


        @ATC also seems to think that encrypting traffic makes it impossible to decrypt the data sets. This is the kind of skill level we are dealing with here.

      3. Shiz0 said on October 16, 2020 at 12:31 am

        And your skill level means not knowing the different between end to end encryption and transport encryption.
        The FF Sync encryption is the former, not the latter like you claim while berating and misinforming others here.
        One can say the implementation may be not secure, one may say to trust mozilla not backdoring it is folish, and i am with that. But the implementation is end to end encrypted, period.
        But with your supposed skill set i am sure you can audit the crypto implementation in no time and publish your 100+ page report paper on it in no time.
        At least then you could bring something of value to this topic.

  2. Bobby Phoenix said on September 19, 2020 at 8:41 pm

    I’ve used sync since it was first available. I’ve never had issues, and I’ve synced new instances of Firefox many times over the years on many different computers and phones. It’s great to know it’s even better now.

  3. Mothy said on September 19, 2020 at 6:22 pm

    Never used the sync service (don’t use/trust cloud based stuff). Instead to sync across devices and as a general backup I copy the Firefox profile folder (see below) to the same directory (C:\My Files) I store all my other data which is then backed up to a local NAS (Network Attached Storage). Then as needed copy the backed up profile over to another system. Not only makes for easy sync without requiring Internet access but also to restore a profile after wiping/re-installing Windows.


  4. Joe Six Pack 99% said on September 19, 2020 at 6:18 pm

    “Syncing is useful to make sure that certain data, say bookmarks and passwords, are always identical between devices that you use”

    Great service!

    I love sending Mozilla Corporation (and their corporate customers) my bookmarks and login details!

    I completely trust them with my most personal data.

    1. ATC said on September 20, 2020 at 9:10 am

      Seriously, if you think that about Mozilla I suggest you just stop using the internet and move out to the desert with your tinfoil hat, and beware the black helicopters.

      1. Iron Heart said on September 20, 2020 at 8:48 pm


        You are a fool if you think that Mozilla is using unbreakable encryption, or that they can’t decrypt the data sets stored on their own(!) server. Are people really that naive?

      2. Anonymous said on September 26, 2020 at 12:45 am

        IronHeart said:
        “You are a fool if you think that Mozilla is using unbreakable encryption, or that they can’t decrypt the data sets stored on their own(!) server. Are people really that naive?”

        I don’t see why Mozilla would do that, even if they had the capabilities. The NSA maybe, it’s their thing, but why Mozilla ? They’re not going to sell passwords on the darknet, they’re paid enough by Google.

        That doesn’t mean that I would trust them with a sync service. When I opt-out of data collection and they install between updates an add-on that collects data anyway (“telemetry coverage”), or when they install a Windows data collection task and don’t even mention it in the release notes, and when this sort of problems keeps happening, showing that it was not an accident, why should I trust anything they say any more ? What fine print did I miss that will make my data unsafe in their hands ?

        We all know how creative those companies are to fool customers. Once trust is lost, there is no coming back.

      3. Anonymous said on September 21, 2020 at 9:49 am

        Fool? Says the guy who spews FUD without any proof to his claims. I’m definitely not for trusting Mozilla unconditionally but what you do certainly isn’t helpful.

      4. Iron Heart said on September 21, 2020 at 12:33 pm


        > Says the guy who spews FUD without any proof to his claims.

        Nice one, I have multiple sources for my claims and have no issue whatsoever presenting them to you upon request. I see no point in posting them over and over again because a comment on some tech site doesn’t have to evolve into a scientific thesis, but I have presented them often enough for you to notice it (though you fail to acknowledge it). You just happen to dislike the things I say, my dude. Nice attempt at discrediting me anyway, though you failed miserably.

        You also failed to consider that Mozilla doesn’t use unbreakable encryption of course, and that they can decrypt data on their servers like anyone else can. Chrome’s phoning home anti-features, for example, also establish encrypted connections… Do you think this makes it impossible for Google to read the data sets? As I said, a folly.

  5. Andy said on September 19, 2020 at 5:21 pm

    I have used FF Sync for years and it usually works well. I sync over about 5 different PC’s using FF. But once in a while I will start up FF, usually on a computer that I don’t use much, and sync will work the wrong way! In other words I expect sync to copy bookmarks from the data base to the PC. So the 2 or 3 week (or month) local bookmarks copy over to the data base. Not sure why it would sync backwards like that.

    When I realize what happens I will go to another of my machines (that I use often) and first disconnect from the net. Then I open FF and copy my (newest) bookmarks to a thumb drive. Then back to the PC that screwed it up and restore that one.

    I hope this new FF sync will be more reliable on syncing the correct way. Also it would be nice to have an option in sync settings on which way you might want to sync.

  6. Anonymous said on September 19, 2020 at 4:24 pm

    Finally! getting tired when I lose some of my histories.

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