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Is this a file renaming problem? What I mean is, if you change the file extension from .gp to .mp4, the video plays normally?

By default, Windows hides some file extensions. You can change a setting in Windows File Explorer to force Windows to show you the extensions: https://support.microsoft.com/en-us/windows/common-file-name-extensions-in-windows-da4a4430-8e76-89c5-59f7-1cdbbc75cb01

I'm using Windows 11 and I'm not sure what version of Firefox. I just got a new computer and downloaded Firefox so I assume its the latest version.

When I save short mp4's from my email or dropbox, Firefox turns them into gp files. I can't use gp files on Facebook or Capcut. I don't want to waste time converting them when they were mp4's to start with. I'm trying to figure out why they are being automatically converted and how to stop that.

If you rename the downloaded files from a .gp file extension to a .mp4 file extension -- without doing any kind of conversion -- do they play normally?

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If you rename the downloaded files from a .gp file extension to a .mp4 file extension -- without doing any kind of conversion -- do they play normally?

I don't know how to do that. I can rename a file, but I don't know how to change it to another type of file. But I'm trying to get this to work automatically so that I don't have to convert every file...or rename them.

jscher2000 - Support Volunteer said

If you rename the downloaded files from a .gp file extension to a .mp4 file extension -- without doing any kind of conversion -- do they play normally?

I don't know how to do that. I can rename a file, but I don't know how to change it to another type of file. But I'm trying to get this to work automatically so that I don't have to convert every file...or rename them.

I understand that we need to solve a problem, but what I don't know yet is whether the problem is Firefox adding the wrong file extension, or the file itself being the wrong format. That is what I'm trying to figure out by changing the file extension. To do that:

(1) Set Windows to show all file extensions per previously linked article

(2) Right-click the file (in Windows File Explorer) and click rename or the rename icon, depending on how your menu displays

(3) Windows will select (blue highlight) the name to the left of the dot, so you need to select the extension to the right of the dot and change it and then confirm when Windows says this might not work.

(4) After changing the file extension from .gp to .mp4, will it play in video players or in a Firefox tab?

Okay, yes. It will let me change the file extension and then all is well. Can we fix it so that I don't have to change it each time?

The possible reasons for Firefox assigning a .gp extension would be something like:

(1) Firefox thinks the website assigned that name to the file. Seems unlikely; even .3gp, an old mobile phone format, is not used any more.

(2) At some point, Firefox stored an association of .gp as the file extension for MPEG video. You can clear stored file associations by renaming a file so that Firefox goes back to basics. Here's how:

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > Help > More Troubleshooting Information
• (menu bar) Help > More Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, on the Profile Folder row, click the "Open Folder" button. This should launch a new window listing various files and folders in Windows File Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > Exit
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then:

Right-click handlers.json then Rename to something like handlersOLD.json

Start Firefox back up again. Then try the MP4 download. Does Firefox use the right file extension?

Note that this will clear your customizations for file actions, for example, whether to show PDFs in a tab or in an external program. For more information on where to re-customize, see: Manage file types and download actions in Firefox.

I did it, but it didn't work. It's still downloading as a gp file.

Is this a public site that others could test (i.e., it doesn't require an account)?