What HTTP response codes do you know?

Main HTTP response codes are divided into several groups:

• 1xx (Informational):

  • 100 Continue — the server has received the initial part of the request, and the client can continue.

• 2xx (Successful):

  • 200 OK — the request was successfully processed.
  • 201 Created — the resource was successfully created.
  • 204 No Content — the request was processed, but there is no response body.

• 3xx (Redirection):

  • 301 Moved Permanently — the resource has been permanently moved.
  • 302 Found — temporary redirection.
  • 304 Not Modified — the resource has not changed, use cache.

• 4xx (Client errors):

  • 400 Bad Request — invalid request.
  • 401 Unauthorized — authentication is required.
  • 403 Forbidden — access is denied.
  • 404 Not Found — resource not found.
  • 429 Too Many Requests — too many requests.

• 5xx (Server errors):

  • 500 Internal Server Error — internal server error.
  • 502 Bad Gateway — incorrect response from upstream server.
  • 503 Service Unavailable — service is unavailable.

Knowing these codes is important for proper handling of responses on the frontend, for example, to display messages to the user or to retry requests.