Status Codes

The Status Code of an HTTP response tells the client whether or not the server was able to fulfill the request. Status codes are 3-digit numbers that are grouped into categories:

• 100-199: Informational responses. These are very rare.
• 200-299: Successful responses. Hopefully, most responses are 200's!
• 300-399: Redirection messages. These are typically invisible because the browser or HTTP client will automatically do the redirect.
• 400-499: Client errors. You'll see these often, especially when trying to debug a client application
• 500-599: Server errors. You'll see these sometimes, usually only if there is a bug on the server.

Here are some of the most common status codes, but there is also a full list here if you're interested.

• 200 - OK. This is by far the most common code, it just means that everything worked as expected.
• 201 - Created. This means that a resource was created successfully. Typically in response to a POST request.
• 301 - Moved permanently. This means the resource was moved to a new place, and the response will include where that new place is. Websites often use 301 redirects when they change their domain name, for example.
• 400 - Bad request. A general error indicating the client made a mistake in their request.
• 401 - Unauthorized. This means the client doesn't have the correct permissions. Maybe they didn't include a required authorization header, for example.
• 404 - Not found. You'll see this on websites quite often. It just means the resource doesn't exist.
• 500 - Internal server error. This means something went wrong on the server, likely a bug on their end.

Don't Memorize

It's good to know the basics by heart, like "2XX is good", "4XX is a client error", and "5XX is a server error". But don't memorize all the status codes... they're easy to look up.

Click to play video