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<Add-on> could not be installed because Firefox cannot modify the necessary file.

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New Contributor

<Add-on> could not be installed because Firefox cannot modify the necessary file.

I see that for the issue:

<Add-on> could not be installed because Firefox cannot modify the necessary file.

The usual fixes include: - ensuring that xpinstall.enabled is set to true - ensuring that extensions.alwaysUnpack is set to true

What might be the non-usual fixes as I have set both to true and I still get the message above.

I have tried installing the <add-on> after I have set the values to true, then again after restarting my browser, then again after restarting my computer and finally tried creating a new profile and repeated each of the steps after setting the 2 preferences to true.

1 REPLY
Site Moderator

Re: <Add-on> could not be installed because Firefox cannot modify the necessary file.

Can you at least update to the latest Firefox 10.0.10 ESR version?

Firefox 10.0.x ESR:


So a new profile with no other extensions didn't work as well?

Which extension is causing this problem or can't you install any extensions at all?