Have you ever tried to install an extension or theme in Firefox and received the irritating “Invalid file hash (possible download corruption)” error message? Now you can work on resolving that problem with the following work-arounds. The Infamous Message Window This is probably the most irritating message window that is associated with installing extensions or themes in Firefox. For whatever reason, you start the installation and get this. Not good at all! So what do you do about it? Possible Work-Arounds Try the following methods to see if one will help get those problem extensions or themes installed. Method 1 – Enable Third Party Cookies

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Method 2 - Manually Install The Extension

Note: If for some reason manually installing the extension or theme still fails, there is a possibility that your anti-virus or another download monitoring software may be corrupting the file. In this case you could download the extension or theme on another computer and transfer it using a flash drive. Method 3 – Clear The Cache

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Method 4 – Restart Firefox After “Failed Add-on Installation”

  • If you are installing directly from the Mozilla Add-ons website, there could be a problem with the Mozilla Add-ons website database or with a broken mirror website. Restart Firefox to see if the extension or theme did install regardless of the“Invalid file hash (possible download corruption)” error message.

Method 5 – Other Alternatives

Hopefully with these tips you can bypass the error and enjoy more Firefox Add-on goodness.