Setup a policies.json for an AppImage of Firefox, to prevent updating Firefox but not the add-ons.

[ivan-hc]

Hi team, I'm developing AppImages on Linux for all 5 development branches of Firefox and the 3 development branches of Thunderbird:

• https://github.com/ivan-hc/Firefox-appimage
• https://github.com/ivan-hc/Thunderbird-appimage

All of them are based on the official archives, with the addition of 4 elements only:

1. the AppRun script (the core of every AppImage)
2. a .desktop file in the root of the AppImage (needed for an AppImage to be validated)
3. an icon still in the root of the AppImage (same as .desktop file at point 2)
4. the policies.json

Well, I have difficult with the policies.json file, it is needed to prevent Forefox/Thunderbird to be updated on their own, or an archive will be downloaded in place, so updates for AppImages should be managed by an AppImage manager or a package manager like my AM.

I have solved this point by adding this to the policies.json file

{
"policies": {
    "DisableAppUpdate": true,
    "AppAutoUpdate": false,
    "BackgroundAppUpdate": false
  }
}

I have seen the https://mozilla.github.io/policy-templates/ page and it seems that "DisableAppUpdate": true is enough to fix this.

Anyway, every time my Firefox updates, I have to manually update my add-ons, and the language (Italian in my case).

I need a tip to made languages updating every time the version changes.

In brief:

1. Firefox/Thunderbird must not be auto-updated, this is a task of external tools, and I have solved this
2. I want that languages and add-ons can update by themself at every update

How should I do?

Thanks in advance.

[mkaply]

I would rather add code to Firefox to detect AppImage and disable updates, similar to what we do for snap, flatpak, and our deb.

How can we know we are in an AppImage?

[Samueru-sama]

@mkaply If you need to detect if you are running as an AppImage you can check if the APPDIR variable is set.

MOZ_APP_LAUNCHER something unrelated, it needs to be set to APPIMAGE because otherwise the desktop entry that firefox makes on its own would point to the binary in the APPDIR (which is a random path) rather than the actual AppImage.

[mkaply]

So I found the bug where we did this for .deb:

https://bugzilla.mozilla.org/show_bug.cgi?id=1799503

We literally just put a file named "is_packaged_app" into the rpm and deb.

Is that something y'all would be willing to do? Would make this really easy.

https://searchfox.org/firefox-main/search?q=is-packaged-app&path=&case=false&regexp=false

[ivan-hc]

Sorry @mkaply , I've tried to understand the discussion in bugzilla and I have seen the searchfox link, but I've not understand.

Should I create a file named is_packaged_app into the AppImage to identify it (and then, I should remove the policies.json file)?

Sorry for my ignorance.

[mkaply]

All good, it was a long discussion.

Yes, I believe that if you just create a file called "is_packaged_app" you can remove policies.json and we'll detect it as not needing to be updated internally.

Based on the code, it looks like in the root of the package.

[ivan-hc]

@mkaply I just did what you said and this is how the about appears

I was not sure and then I repeated the test by packaging an old Firefox 140, to see if it updates

I can't see the loading of an update, and this is good.

So all I need to do is to create an empty file named is_packaged_app in the root then?

Does this work also with Thunderbird?

[ivan-hc]

According with this solution, I edited the scripts like this

• ivan-hc/Firefox-appimage@c0160d3
• ivan-hc/Thunderbird-appimage@1091674

It is enough to run

touch "$APP".AppDir/is_packaged_app

...in the script. I removed the "policies" part. All as you suggested @mkaply , thank you.

[mkaply]

That's great everything worked!

[ivan-hc]

Solved then 😄

[ivan-hc]

@mkaply I'm here again, I just updated my Firefox AppImage to v144 from v143.0.4, this is what happens

I still need to update the language pack manually

[mkaply]

For the flatpak, we bundle all the languages to solve this problem.

https://support.mozilla.org/en-US/kb/deploying-firefox-language-packs

But you can put the language packs in subdirs so they don't all get loaded (I think).

So like italian would go in a subdirectory named the same as the language pack with locale prepended (locale-it-IT)

I'm sidetracked right now, but I take a look at this in the next couple weeks if you can't figure it out.

[ivan-hc]

For the flatpak, we bundle all the languages to solve this problem.

No, the AppImage recognizes the system language requirement upon first launch, and appears under Languages ​​as available, but it isn't automatically installed (I have to set it up myself, which I think is normal, since I download the generic package, in English) or updated (this is the issue).

I'm curious to see how I can implement all the language packs automatically, hoping the Firefox AppImage doesn't get too big (it's only 89 MB now).

Add-ons also don't appear to update automatically.

[mkaply]

Interesting. I thought we did all languages.

Things definitely should update eventually. I thought we had added code to automatically update language packs...

[ivan-hc]

@mkaply in this video I download this old Firefox AppImage.

https://github.com/ivan-hc/Firefox-appimage/releases/download/20251002-233003/Firefox-stable-143.0.3-x86_64.AppImage

The .config and .home directories near the AppImage are needed to isolate the AppImage and not to contrast the runninf Firefox (AppImage) already on the system.

You can see that it is full English, and it detects that Italian is recognized. I need to enable it manually.

simplescreenrecorder-2025-10-15_19.12.11.mp4

But now see here. I will update it using delta updates (appimageupdatetool). When I run it again, I need to update the language manually.

simplescreenrecorder-2025-10-15_19.18.01.mp4

That's all.

[mkaply]

I think the language would have updated after some period of time (probably only an hour or so)

I think the issue is that regular Firefox updates check for language pack updates, but because the update came from outside Firefox, it didn't check for a new language pack on startup/update.

[mkaply]

I don't know why they would add that. It just seems like it would prevent updates from happening at all. Unless somehow they've setup their own internal update servers?

If you update extensions using this in addons:

Does it update the language pack?

[ivan-hc]

If you update extensions using this in addons:

Does it update the language pack?

Yes, I did it in the second video, at minute 1:10

[mkaply]

I noticed your about says "Updates disabled by your organization" Did you put a policies.json back?

At it's core, I think this is probably a Firefox bug. We should have checked for updates to the language pack as soon as we detected we are a later version of Firefox (regardless of how we got there).

[mkaply]

https://bugzilla.mozilla.org/show_bug.cgi?id=1724360

[ivan-hc]

I noticed your about says "Updates disabled by your organization" Did you put a policies.json back?

Yes, I restored it after updating to Firefox 144, because the bug had recurred. So I'm testing both behaviors.

In particular, when I tried to update the add-ons manually, it showed that Tampermonkey hadn't been updated. So I assumed both the language packs and add-ons I have weren't receiving updates.

I emphasized that I added the policies.json file and removed the is_packaged_app file only after I noticed the problem had recurred.

https://github.com/ivan-hc/Firefox-appimage/blob/790737005d651b9183ef3b93f6e66e4e3f58bdfc/firefox-builder.sh#L374-L383

This snapshot was the first with Firefox 144 and the is_packaged_app (and no policies.json)

https://github.com/ivan-hc/Firefox-appimage/releases/tag/20251014-134958

...I readded the policies.json file and removed the other one in the last snapshot

https://github.com/ivan-hc/Firefox-appimage/releases/tag/20251015-035012

[mkaply]

So it would appear that we have a larger bug with language packs not updating going from 143 to 144, so I think you just ended up in that. I would wait until we've figured it out.

[ivan-hc]

OK, I'll wait

[mkaply]

We're still looking at the langpack problem, but I got the name of the file wrong.

is-packaged-app

It won't say anything in the about dialog.

[ivan-hc]

We're still looking at the langpack problem, but I got the name of the file wrong.

is-packaged-app

It won't say anything in the about dialog.

should I bundle it again with that file then?

[ivan-hc]

should I bundle it again with that file then?

I just reverted my last change, I restored the is_packaged_app file and removed policies.json

• ivan-hc/Firefox-appimage@80a0089
• ivan-hc/Thunderbird-appimage@b5ac20f

Builds will be ready in few minutes.

[mkaply]

Yes, is-packaged-app. things will make more sense (you'll see no message in the about dialog)