HTTP status codes explained: what 200, 301, 404 and 503 mean

Every time a browser asks a website for a page, the server answers with a three-digit status code before it sends anything else. Most of the time you never see it. When something goes wrong, it is often the only clue about whose fault it is.

The five families

The first digit tells you the general story.

• 1xx, informational. The server is working on it. You almost never see these.
• 2xx, success. The request worked. 200 OK is the one you want.
• 3xx, redirection. The page has moved and your browser should go somewhere else. 301 is a permanent move and 302 is a temporary one.
• 4xx, a problem with the request. The server is up, but it will not give you that page. 404, 403 and 429 live here.
• 5xx, a problem on the server. The server could not do what you asked. 500, 502, 503 and 504 live here.

The ones you will meet most

• 200 OK: the page loaded normally.
• 301 Moved Permanently: the address has changed for good. Search engines transfer the old address’s standing to the new one.
• 302 Found / 307 Temporary Redirect: the page is somewhere else for now. Common for login steps and short-term campaigns.
• 304 Not Modified: your browser already has the latest copy, so nothing was sent again. This is what makes repeat visits fast.
• 400 Bad Request: the server could not understand the request, often because of a broken cookie or a malformed address.
• 401 Unauthorized: you need to sign in first.
• 403 Forbidden: the server understood you but will not let you in. See below.
• 404 Not Found: there is nothing at that address. Read more in What does a 404 mean?
• 429 Too Many Requests: you, or a network you share, have made too many requests too quickly. Wait a few minutes.
• 500 Internal Server Error: something broke on the server. More on the 5xx errors.
• 502, 503, 504: a gateway, overload or timeout problem between the servers that run the site.

Why 403 deserves a mention

A 403 usually means the site is working fine and has chosen not to serve you. Typical causes are a security rule that blocks your country or network, a firewall that flags automated traffic, or a page that needs an account. Our checker reports a blocked request as Inconclusive rather than Down, because the site is clearly answering.

What it means for site owners

Search engines read these codes too. A page that returns 200 but shows an error message (a “soft 404”) confuses them. A 5xx that lasts for days can make a page drop out of search results. Return the code that tells the truth.

Want to see the status code a site returns right now? Run a check: the result shows the HTTP code, response time and redirect chain.

Related guides

• What does a 404 Not Found error mean, and how do you fix it?
• 500, 502, 503 and 504 errors: what server errors mean
• Website not loading? A step-by-step checklist

Last updated 2 November 2026. Written by the siteupdown.com team. Spotted a mistake?

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