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HTTP Status Codes Explained: From 200 to 500

A quick guide to understanding what those error or success codes your browser and server constantly exchange mean.

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Every time you visit a web page, your browser and the server have a little conversation. The server responds with a 3-digit numeric code: the HTTP Status Code.

Main Categories

  • 1xx (Informational): “Request received, processing”.
  • 2xx (Success): “Everything went well”. The famous 200 OK.
  • 3xx (Redirection): “The page moved”. 301 (Permanent) or 302 (Temporary).
  • 4xx (Client Error): “You did something wrong”.
    • 400 Bad Request: Invalid request.
    • 401 Unauthorized: You need to log in.
    • 403 Forbidden: Logged in, but no permissions.
    • 404 Not Found: Page does not exist.
  • 5xx (Server Error): “I (the server) failed”.
    • 500 Internal Server Error: Generic error.
    • 502 Bad Gateway: Communication error between servers.

Understanding these codes is crucial for debugging any web application and improving your site’s SEO.

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