How To Fix "Content Encoding Error" on Mozilla Firefox

Some times during surfing on different websites in some websites will show up this message: "Content Encoding Error The page you are trying to view cannot be shown because it uses an invalid or unsupported form of compression.", the website which has been clicked to be open shows this message in place to be opened as usual.

This "Content Encoding Error" is some kind of error or a way which Mozilla tries to protect their costumers computers, i do not have the information about this but i know how to remove this annoying message from Mozilla Firefox browser.

To remove this must delete the Cache of Mozilla Firefox browser, by going at Tools then open Advanced and click on Network, there will find the cache and delete button, after cache has been removed open another tab on Mozilla browser and click at Url place only this about:support and restart Mozilla Firefox browers.

If this way does not works then must delete the cache folder of Mozilla Firefox browser manually, open My Computer and go at C:\Users\<user>\AppData\Local\Mozilla\Firefox\Profiles\<profile>\    

I got the same error message and only by deleting cache and restarting browser error message did not showed up again, anyway if this does not help try to visit this reply of Mozilla about Content Encoding Error Issue.

If this way does not solve this problem and on your browser you keep seeing the same "Content Encoding Error The page you are trying to view cannot be shown because it uses an invalid or unsupported form of compression." then is another alternative way to solve this problem. Follow these instructions carefully, and do exactly what is written on this tutorial, otherwise might have bigger problems with Mozilla Firefox browser, because this way is to edit manually encoding of Mozilla Firefox.

1. Open Mozilla Firefox browser and at address bar write about:config
2.  Click on "I'll be careful, I promise" button and mark "Show this warning next time" 
3. At Search Address write encoding
4.  Double click on network.http.accept-encoding
5. Change 'String Value' from  gzip, deflate to true
6. Close the browser and see the result.

This will remove the "Content Encoding Error" after your browser is closed and has been reopened. 


  1. Check your antivirus also, sometime it's make that kind of issue

  2. It work! I followed the about:config procedure. THanks.


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