Here I'll list the important ones you should know. For everything else, there is HTTP Cats.

The 200s are success codes. It means your GET request was successful, or your POST request was successful and a new account was created, etc.

• 200 OK
• 201 Created - usually after a POST

The 300s are all about redirection. It's still a success, just means that the resource has moved somewhere else.

• 301 Moved permanently
• 302 Found - usually a temporary redirect

The 400s are about bad requests. Anything 400 or higher is an error.

• 400 Bad request
• 401 Unauthorized - usually when you aren't logged in or you haven't supplied some Authorization header
• 403 Forbidden - you're logged in/authenticated, but you don't have access (maybe the route is only for admins)
• 404 Not found

The 500s are about server errors.

• 500 Internal server error - some error occurred on the server.