This error is occurring on a Windows 10 machine.

My guess is when you follow a link to somefile.accdb you expect Firefox to show a download dialog with the option to open it in MS Access or save it to disk. Does that sound right?

You mentioned an error -- what is the message you get?

By the way, when you choose Open with [application], Firefox would not hand off the URL to Access to open, it would download the file to the Windows TEMP folder and pass that path to Access.

I just remembered that Access -- at least the version from Office 365 -- adds a new protocol to the Windows Registry. If a link starts with ms-access: then Firefox should ask what external application you want to use to open the link and suggest using MS Access by default.

I'm unable to get the error at this time. I tried to remote into my machine at work and the link worked. So I will have to get that for you tomorrow from my computer at work.

This is the other message we are getting. It says we tried to open but only lets us save. I was unable to get the error to show again.

We got there in a roundabout way. First, save the accdb file. Next close Firefox. Open Firefox and to options, applications. For Access choose Access (Default). Close Firefox. Open Firefox. Go to Options, Applications. For Access click on use other program. Choose Access. Close that window and close Firefox. Open Firefox. Go to Options, Applications. for Access Change from Access (Default) to Microsoft Access. Close Firefox. Open Firefox and it should work.

It seems a little frustrating. There's no easy way to add a file type (extension). And there's no way to remove one from the list unless you choose troubleshoot and do a Tuneup.

This is the other message we are getting. It says we tried to open but only lets us save. I was unable to get the error to show again.

This message is common for "executable" type files; usually those cannot be set to have an Open option and must always be saved.

But I see from your later reply that after saving one ACCDB file, it appeared on the Options page. Firefox discovered that the files can be opened with MS Access and listed the option there. I don't know why it didn't discover that on the first click (from a Windows Registry search) -- I think that is what usually happens when Firefox encounters a novel file type. ??

These preferences are stored in Firefox's handlers.json file in your profile. In theory, it's editable in a text editor, but users have reported mixed results. Should you need to reset the download handlers back to default, you can go into the profile folder and remove the handlers.json file (while Firefox is not running). More info on locating the profile folder: Profiles - Where Firefox stores your bookmarks, passwords and other user data.

In the handlers.json file its kind of difficult to tell where one entry ends and where another begins it all seems to be one continuous line of text.. I can see where pathway to the Access .exe is and I see the extension .accdb, but I don't really understand how the text around it works. Could you please provide an example of what an entry for one application would look like? Thanks.

Yes, it is all saved as one line. If you open the handlers.json file in a Firefox tab, after a moment it will display in a structured view. That should give you an idea of how the data looks to Firefox, but I have not seen a good explanation of what everything means or what overrides what, which is why we generally don't suggest editing it.

Theoretically, we could make a backup copy of the handlers.json file and give it a try. If it doesn't work, just overwrite it with the backup and we would be back to where we were, no?

Theoretically, we could make a backup copy of the handlers.json file and give it a try. If it doesn't work, just overwrite it with the backup and we would be back to where we were, no?

Yes.

It turns out that if you even change one thing in the handlers.json file the whole profile gets corrupted. There was an error saying something about using an older profile that was corrupt. Good thing I had backed up the whole profile prior, I would have lost bookmarks, passwords, and lots of other settings.

It turns out that if you even change one thing in the handlers.json file the whole profile gets corrupted. There was an error saying something about using an older profile that was corrupt. Good thing I had backed up the whole profile prior, I would have lost bookmarks, passwords, and lots of other settings.

That's strange, since it's only one file and other people have edited it successfully. Someone should test this more thoroughly to see where the fragility is.