HTTP Status Codes
Searchable reference of HTTP status codes 1xx to 5xx: meaning, when to use each, common causes, SEO impact and a sample response. Look up a number or status line.
How to use HTTP Status Codes
- 1Browse the list, tap a class chip such as 4xx, or type a number or word into the search box.
- 2Open a code to read what it means, when to use it, what usually causes it and its SEO impact.
- 3Switch to Lookup to paste a number or a full status line from a response and get the explanation.
What makes it better
- All registered codes from 100 to 511, including 418, 421, 422, 425, 426, 428, 429, 431, 451 and 506 to 511
- 306 is marked unused and 418 is marked as the April Fools' RFC 2324 joke
- nginx and Cloudflare codes (444, 499, 520 to 527, 530) are in their own non-standard group
- Each code has a sample response, with the Location header for redirects and Retry-After where it applies
- Open the page with #404 in the address to jump straight to a code
About HTTP Status Codes
This reference lists the status codes in the IANA registry, from 100 Continue to 511 Network Authentication Required, each with a plain-language meaning, when to use it, common causes, how search engines treat it and a typical response. Filter by class, search by number or word, or switch to Lookup and paste a status line such as HTTP/1.1 404 Not Found. Common non-standard codes from nginx and Cloudflare are shown in a separate, labelled group.
Common uses
- Decide between 301 and 302, or 404 and 410, when removing or moving a page.
- Work out why an API call returns 422 or 429 and what the client should do next.
- Explain a 5xx error from a CDN or proxy to a non-technical colleague.
- Check how a status code affects crawling and indexing before a migration.
Example
Input
404
Result
404 Not Found Class: 4xx Client error Defined in: RFC 9110 §15.5.5 What it means: The server cannot find anything at this URL. It does not say whether it is gone for good. When to use it: The URL never existed or the page was removed, and there is no better page to send people to. Serve a helpful error page that still returns 404. Common causes: A typo, a deleted or renamed page, a broken link or an incorrect rewrite rule. SEO impact: Not indexed, and pages that return 404 drop out of search results over time. A few 404s are normal. Fix broken internal links and redirect pages that had traffic or backlinks. Example response: HTTP/1.1 404 Not Found Content-Type: text/html; charset=utf-8 <h1>Page not found</h1>
Good to know
- The SEO notes follow how Google documents handling of these codes. Other search engines are similar but not identical, and the guidance can change.
- The reason phrase after the number (Not Found, Forbidden) is only a label. HTTP/2 and HTTP/3 do not send one, and clients act on the number.
- Codes marked non-standard are not in the IANA registry. Their meaning depends on the software that sends them, so check that product's documentation.
HTTP Status Codes FAQ
What do the five classes of HTTP status codes mean?
1xx codes are informational, 2xx mean success, 3xx are redirects, 4xx mean the client made a mistake and 5xx mean the server failed. If a client sees a code it does not know, it treats it like the x00 code of that class.
What is the difference between 301 and 302 redirects?
A 301 says the move is permanent, so search engines swap the old URL for the new one and pass its signals along. A 302 says it is temporary, so the original URL normally stays indexed. 308 and 307 are the same pair but keep the request method.
Is a 404 or a 410 better for a deleted page?
Both remove the page from search results. 410 says the removal is deliberate and is dropped slightly faster, while 404 only says nothing was found. If the page has a close replacement, a 301 redirect to it is better than either.
Which status code should I use during maintenance?
Send 503 Service Unavailable with a Retry-After header. It tells browsers and crawlers the outage is temporary, so search engines keep your pages indexed instead of treating them as removed. Do not serve a maintenance page with 200.
What is a soft 404?
A soft 404 is a page that says not found but returns 200 OK. Search engines may index it or report it as an error in Search Console. Make missing pages return a real 404 or 410 status.