HTTP Status Codes and Reason Phrases

Every request sent by an HTTP client causes one or more responses to be returned by the server that receives it. As you saw earlier in the discussion of the Response message format, the first line of the response is a status line that contains a summary of the results of processing the request. The purpose of this line is to communicate quickly whether or not the request was successful and why.

HTTP status lines contain both a numeric status code and a text reason phrase. The reason for having both a number and a text string is that computers can more easily understand the results of a request by looking at a number and then can quickly respond accordingly. Humans, on the other hand, find text descriptions easier ...

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