Response codes

The first line of the HTTP response is the state drain. It consists of two parts: a three-digit number (response code) and a text message (response description).


The client learns the status of its request from the response code and decides what to do next. Examples of different responses from the server:

201 Created
401 Unauthorized
507 Insufficient Storage

Response codes are divided into 5 categories. The first digit of the response code determines which category it belongs to.

All answers starting with the number 1 are classified as informational. We will not talk about them in detail ...

Response code 200

After all, there are others that are much more interesting to us. All responses that look like 2xx are successful. The response most loved by programmers is 200 OK , which means that everything is fine, the request was successfully completed.

You may also find this list of other “good” answers helpful:

Code Line Description
200 OK Fine
201 Created Created
202 accepted Accepted
203 Non-Authoritative Information Information is not authoritative
204 no content No content
205 Reset content Reset content
208 already reported Already reported

Response codes 301, 302

Responses that look like 3xx are in the redirect class . They indicate that the resource has been moved to another location.

The most popular of them:

  • 301 - moved permanently
  • 302 - moved temporarily

In the colloquial speech of programmers, you will often hear “302 redirect” or “301 redirect” - this is just about it.

Full list of 300 replies:

Code Line Description
300 Multiple Choices many options to choose from
301 Moved Permanently moved forever
302 Moved Temporarily moved temporarily
303 See other watch other
304 Not Modified did not change
305 use proxy use proxy
307 Temporary Redirect temporary redirect
308 Permanent Redirect permanent redirect

Response code 404

All answers that start with the number 4 indicate a client-side error , and there are a lot of them. The most popular you know for sure: this is the answer “404 - not found”.

Other common answers are given in the table:

Code Line Description
400 Bad Request invalid request
401 Unauthorized not authorized
402 Payment Required payment required
403 Forbidden forbidden
404 not found not found
405 Method Not Allowed method not supported
406 Not Acceptable unacceptable
407 Proxy Authentication Required proxy authentication required
408 Request Timeout timed out
413 Payload Too Large payload too large
414 URI Too Long URI is too long
429 Too Many Requests too many requests
499 Client Closed Request the client closed the connection

Response code 501

And finally, the last category is server-side errors. All such errors start with the number 5. The most common error for a developer is 501 (functionality not implemented). Sometimes it happens.

In general, get acquainted with these error codes, they are now your friends for the rest of your life. Well, as usual, here is a table with the most useful error codes on the server side:

Code Line Description
500 Internal Server Error Internal Server Error
501 Not Implemented not implemented
502 Bad Gateway wrong gateway
503 Service Unavailable service is unavailable
504 Gateway Timeout gateway not responding
507 Insufficient Storage storage overflow
508 Loop Detected endless redirect
509 Bandwidth Limit Exceeded channel bandwidth exhausted
520 unknown error Unknown error
521 Web Server Is Down web server not working
522 Connection Time Out connection not responding
523 Origin Is Unreachable source unavailable
524 A Timeout Occurred timeout expired
525 SSL Handshake Failed SSL handshake failed
526 Invalid SSL Certificate invalid SSL certificate