Profile used with a newer version of Firefox

[joe9351]

Every so often upon closing firefox 125.0.3 this error occurs:

The last time I created a new profile, I lost all my data. So I would like to have the correct procedure to create a new Profile in Firefox.

Or is the error a scam?

[jscher2000]

Sorry to hear about this problem. A new profile is a fresh start, but your old profile is still there.

After letting Firefox create a new profile, you can load the About Profiles page by typing or pasting about:profiles in the address bar and pressing Enter/Return to load the list. It's difficult to test which profile you were using immediately before the current one, but I think they are listed in order of creation, so that's one clue.

To determine which version of Firefox was last to use a profile, find the Root Directory row and click the Open Folder button. Find the compatibility.ini file and open that in a text viewer (like Windows Notepad). Note that Windows may hide the .ini file extension to make your life more mysterious, but there's only one file named compatibility.

Typical file content would be along these lines:

[Compatibility]
LastVersion=125.0.3_20240425211020/20240425211020
LastOSABI=WINNT_x86_64-msvc
LastPlatformDir=C:\Program Files\Mozilla Firefox
LastAppDir=C:\Program Files\Mozilla Firefox\browser

You can compare what you see in your next-to-last profile with your new one. Where is the mismatch?

[joe9351]

I know how to get to the profiles folder, But I think you want Firefox to create a new profile. But that I am reluctant to do because once before I did that and I lost MY data , Passwords etc.

So If you could direct me to instructions to create a new file, It would be appreciated.

[jscher2000]

Creating a new profile doesn't erase the old one.

I'm not sure what you mean by "create a new file." If you mean a new profile, Firefox will do that automatically.

Can you get to the compatibility.ini file right now, based on your knowledge of profile fold

[joe9351]

Yes:

latest
[Compatibility]
LastVersion=125.0.3_20240425211020/20240425211020
LastOSABI=WINNT_x86_64-msvc
LastPlatformDir=C:\Program Files\Mozilla Firefox
LastAppDir=C:\Program Files\Mozilla Firefox\browser

Previous
[Compatibility]
LastVersion=125.0.3_20240425211020/20240425211020
LastOSABI=WINNT_x86_64-msvc
LastPlatformDir=C:\Program Files\Mozilla Firefox
LastAppDir=C:\Program Files\Mozilla Firefox\browser
InvalidateCaches=1

Except for InvalidateCaches=1 There is no difference that i can see.

What is this XULRunner and could it be wrong?

[jscher2000]

XULRunner is a component that launches Firefox. It might be the first thing that runs when you launch Firefox.

Since the versions match, try switching profiles using the About Profiles page -- here's how:

• Type or paste about:profiles in the address bar and press Enter/Return to load the page
• Click the "Launch profile in new browser" button for your previous profile to test whether Firefox can run it -- hopefully it can since it's the same build
• If that works, click the "Set as default profile" button for that one -- this will take effect at the next startup
• You're done with this page

[joe9351]

I'm not sure if I can try that because all the earlier profiles are Beta profiles? And some of the profiles have very few Items in them.

[joe9351]

I found in a search that when firefox closes normally The parent.lock file is deleted.

I wonder if this is true. Because I always close firefox with theX.and

I have 3 firefox profiles:

The latest one, one day older, two days older

all have parent.lock still in them,Of course firefox is not runing.

I have removed 4 or 5 profile folders that had only the parent.lock file in them. Firefox seems to be working fine. Not sure if the XULrunning error still occurs.

[ystk_k_fr_pr_]

I had to create new profiles since firefox was updated from 120 to the later. When trying to launch my older profiles in updated firefoxes. it cannot get launched. later versions upto 126.

Edit. I also had to create new profiles.

[joe9351]

ystk_k_fr_pr I do not get the error pictured in your post.

 But it seems to me that If firefox is installing updates, the update should create a new profile to go along with the update.

[candyomg]

Running Firefox on Windows 10 Pro. My current setup includes 3 different Firefox Browsers: Original, Developer, and Nightly. I've created a new profile for original Firefox, but am still seeing the XUL Runner Error mentioned in this thread. I have even tried to create a new profiles folder to house the old profiles to ensure the existing profiles don't interfere with the new profile. This didn't seem to help either. All the versions I have do opens and seemingly work fine, however, I'm just tired of the pesky XUL Runner error. Any suggestions beyond the ones listed?