The response “ 406 Error – Not acceptable ” is not as common as a “404-Page not found” but does happen occasionally and should be fixed.
What causes a 406 Error
When you click a page link or access a website, your browser sends a request to the host server. In other words Chrome (for example) requests information (access) from example.com. When sending this request, the browser also informs the server what formats it accepts in return by including an “Accept Header”.
If we were writing in plain language, it would be something like: “Hello, my name is browser. I would like to know more about your page. Please send info in return. I accept such and such formats”.
If the returned response is “406 Error– Not acceptable”, it means the browser does not support a format sent by the server or the request is in violation of some settings.
Accept Headers commonly behind 406 Error
Accept-Charset and Accept-Language
Character set is the method by which tables convert code into readable characters. It mainly covers languages and symbols.
At the beginnings of time, the commonly used table was ASCII. However, ASCII doesn’t include characters used in many countries. The need to decode such characters required the switch to a broader table. Standard is now ISO-8859 to support international symbols and alphabets, though the list includes many more.
The Accept-Encoding header lists the HTTP compression methods the user agent accepts. A 406 Error – Not Acceptable will return if the file format is not supported by the server. Accept encoding headers commonly used include gzip, deflate, compress..
HTTP compression is necessary to compact files so they travel between server and browser without drastic loss of speed.
A request can specify that only data within a certain range of bytes be included in the response. In that case only a portion of what is available will be delivered back.
It can also happen that a server has set security parameters that a request violates, Mod_security, a firewall program running on Apache server.
Fixing 406 Error – Not Acceptable
When a 406 Error occurs, the first sources to investigate are the Accept-Headers by either accessing the source code or requesting the developer to check them.
With the web being truly worldwide and giving access to the most obscure information (while still interesting and needed by the searcher), you need to make sure you are set to be visible. If you think the headers are responsible for such error, scan your coding and make sure you are set for acceptable mimes.
In case the response violates security settings, they can be disabled (though they may have been implemented for a reason). It is recommended to check with the provider to avoid conflicts.
If the response 406 Error- Not Acceptable occurred while working on WordPress, you can get information on fixes through this support forum.
406 Error – Not Acceptable doesn’t happen often, mostly because any type of character or data is accepted by browsers nowadays. However, it can pop up, in which case the query is left unsatisfied and you count one less visitor that day.