OpenCart ERR_CONTENT_DECODING_FAILED is a very serious Error that can be down your website or web pages. Basically, this kind of problem can be come whenever you enable the GZip Compression or mis-configuring the code of enabling or disabling the GZIP compression. This compression is important when you want to increase the page loading speed of your website.
ERR_CONTENT_DECODING_FAILED

I got this error one of the my client website and i tried everything but not able to figure out how to solve this error. I google about it and tried everything but doesn't work for me. After few days, i am just exploring the admin panel of client website and found some option that is about server and server errors. I solved the error by changing settings in admin panel and i am here to explain how can you solve this issue just by changing settings from OpenCart admin panel.

Method 1: Disable Compression 

This error most likely is a compression error so we'll play with the compression settings
  1. Go to OpenCart Admin Dashboard
  2. Navigate to System > Settings
  3. Click on Edit button of store
  4. Goto Server Tab and Look for "Output Compression Level"
  5. Enter 0 into it
  6. Now your website is working
OpenCart Admin Panel - Click to View Full Size


Method 2: Disable Error

If you want to keep compression for your website then you can try this method may be it can be solve your problem.
  1. Go to OpenCart Admin Dashboard
  2. Navigate to System > Settings
  3. Click on Edit button of store
  4. Goto Server Tab and find "Error Handling" section
  5. Set No for Display Errors
  6. Check your website
Both methods worked for me, if you are facing problem after trying one of the above method then i will recommend you to try both method and after that check your website. If you are still facing the problem then you can contact me anytime and i will try to solve your issue.