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Firefox is adding a .part extension to my downloads and they won't open. Why?? Fix???


When I download a file, Firefox does 2 things: changes the file name to gobbledy-gook of letters and numbers, AND, adds a .part extension -- therefore the files won't open. This is a NEW problem. If I manually remove the .part extension in the download folder, the file will open, but I still have the problem of the name change. I believe that the .part extension is supposed to go away when the download is finished, but that does not happen. Also, my downloads always used to come with their original name, not a numbers/letters name. Thoughts?

Chosen solution

Do you have any security (anti-virus) software installed that may be causing this?


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  • Top 10 Contributor
2347 solutions 20809 answers

It sounds as though the download process is not completing. Does anything in this article help? What to do if you can't download or save files

Also, your system information did not list any extensions. Have you installed any downloaders or security filters lately that might affect how Firefox downloads files?

  • Top 10 Contributor
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Chosen Solution

Do you have any security (anti-virus) software installed that may be causing this?


Mitchina 0 solutions 1 answers

I also have this problem with Firefox - but I had turned off my entire security software for these downloads so that was NOT the problem. I fixed this by just using Explorer - seems I need explorer more and more because Firefox is limited and provides little to no help in the way of fixing these things. Tell me now, what is the problem is it is NOT the security software, hm?

  • Top 10 Contributor
2347 solutions 20809 answers

Helpful Reply

Hi Mitchina, which problem do you have -- the .part file not being renamed to the final correct name, or a different problem?

Did you try turning off the scanWhenDone setting? For clarity, here are the steps in full:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the filter box, type or paste scan and pause while the list is filtered

(3) Double-click browser.download.manager.scanWhenDone to toggle its value from true to false.

What this does: Normally Firefox submits the file to your AV software for an on-demand scan. Toggling this setting turns that off. It also prevents Firefox from adding a notation to the file that the source of the file was the internet. That may change how Windows treats the file. You should turn your real-time AV scanning back on when you have this feature turned off.

If that doesn't help, there could be a permissions problem with the download folder, or another issue that doesn't come immediately to mind, but we need more information from you.