HTTP Status Code Lookup

Status code

Result

NameMoved Permanently
What it meansThe resource has permanently moved to the URL in the Location header.
Family3xx — redirection
Effect on indexingPasses signals to the new URL; the correct code for a permanent move.
Cachingcacheable by default
Code301

The first digit says most of it

Explains a server response code, its family, its effect on indexing and its default caching behaviour.

Response codes group by their first digit: 2xx is success, 3xx is redirection, 4xx is a client error, 5xx is a server error. That alone tells you which direction the problem lies in before you know any detail.

Only a few matter for search, but those few matter a great deal. 404 against 410 decides how fast a page leaves the index, 503 against 500 decides whether a site keeps its rankings through maintenance, and mass 403s from a blocked crawler are the commonest cause of a sudden traffic collapse.

What this calculator shows

The name and meaning of the code
The family it belongs to
Its effect on indexing and on caching

What to keep in mind

The reference covers the codes that actually occur on the web rather than the full RFC list.
Caching behaviour is the default; Cache-Control and Expires headers override it.

FAQs

404 or 410 — which is better?

410 removes a page from the index faster, because it means permanent deletion. A 404 leaves open the possibility that the page returns, so crawlers keep checking for a while.

What code should I serve during maintenance?

503 with a Retry-After header. It tells the crawler to come back later and does not cost you index coverage, unlike a 500 or a 404.

Why do crawlers get a 403?

Usually a bot-protection layer or a firewall that failed to recognise the crawler's User-Agent. Check it with the URL inspection tool in a webmaster console.

Is a single 500 dangerous?

No, crawlers come back later. What is dangerous is sustained 5xx: after a few days pages start dropping out of the index.

Worked example

The most asked-about code

Input: 301

Output: Moved Permanently, family 3xx, passes signals to the new URL

Note: Browsers cache it by default and for a long time. Which is why a misconfigured 301 is so painful to undo: visitors' browsers remember it even after the server-side rule is gone.

Useful links

All tools in Dev Tools

HTTP Status Code Lookup

Result

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