These are some of the most common HTTP codes that everyone working or building servers should know. Here is high level meaning of codes. I'll go more in depth later.
- 1xx - Informational
- 2xx - Success
- 3xx - Redirect
- 4xx - Client Error
- 5xx - Server Error
200 OK #
The most common HTTP code, indicates success of request. Response may vary based on request method used.
201 Created #
Means that request to create resource has been fulfilled.
301 Moved Permanently #
This and all future request should be redirected to given URL.
303 See Other #
When received as response from POST (or similar) request, client presumes that request was successful and redirects to given URL (using GET method).
307 Temporary Redirect #
This request should be redirected to given URL but future requests should still use original URL.
400 Bad Request #
Request can't be processed because of invalid request syntax, size, ...
403 Forbidden #
Request is valid but server refuses action due to lack of necessary permissions for resource or invalid credentials. The request should not be repeated.
404 Not Found #
The requested resource could not be found.
429 Too Many Requests #
Used for rate limiting. User has sent too many requests in a given amount of time.
500 Internal Server Error #
Generic error message that indicates error in request processing on server side.
503 Service Unavailable #
Server cannot handle request due to overload or maintenance. Usually temporary.
There are much more status codes available, especially 4xx for all kinds of specific needs. I encourage you to learn more on Wikipedia.