What is the difference between 401 and 403?

401 Unauthorized means the request has no valid credentials, so logging in may help. 403 Forbidden means the server understood who you are and still refuses the request.

Which status code should I use for a redirect?

Use 301 or 308 for a permanent move and 302 or 307 for a temporary one. 307 and 308 keep the original HTTP method, while 301 and 302 may turn a POST into a GET.

What does a 5xx error mean?

A 5xx code means the server failed to handle a valid request. It is the site's problem, not yours, and retrying later is usually the right move.

HTTP status codes

An HTTP status code is the three-digit number a server sends back with every response. It tells the browser, or your code, whether the request worked, moved, failed because of the client, or failed because of the server.

The first digit gives the class: 1xx informational, 2xx success, 3xx redirection, 4xx client error and 5xx server error. Pick any code below for what it means and what to check first.

HTTP status codes

1xx · Informational

2xx · Success

3xx · Redirection

4xx · Client error

5xx · Server error

MDN reference

How to use it

Find the code in the list, or search by number.
Read the meaning and the tips for the usual causes.
Open the code's page for an example response and related codes.

This tool is also built into Zest search, so you can type your question into the search box and get the same answer above the results.

Common questions

What is the difference between 401 and 403?: 401 Unauthorized means the request has no valid credentials, so logging in may help. 403 Forbidden means the server understood who you are and still refuses the request.
Which status code should I use for a redirect?: Use 301 or 308 for a permanent move and 302 or 307 for a temporary one. 307 and 308 keep the original HTTP method, while 301 and 302 may turn a POST into a GET.
What does a 5xx error mean?: A 5xx code means the server failed to handle a valid request. It is the site's problem, not yours, and retrying later is usually the right move.