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What the HTTP Status Code Lookup does
The HTTP Status Code Lookup explains what a response code means. Type a number such as 404 to see its name, class and a one-line description, or type part of a name, such as timeout or redirect, to list every matching code. The page covers the 28 codes you meet most often in real APIs and websites.
The first digit gives the class: 1xx informational, 2xx success, 3xx redirection, 4xx client error (something is wrong with the request) and 5xx server error (the request looked fine but the server failed). Knowing which side is at fault is usually the first step when debugging a failed call.
When to use it
- Reading an error in browser DevTools or a log line and deciding whether the bug is in the client or the server.
- Choosing the right code for a new API endpoint, such as 201 after creating a resource.
- Setting up redirects for a site migration and choosing between 301, 302, 307 and 308.
- Handling rate limits correctly by recognising 429 and backing off.
Worked example
Input
429Output
429 Too Many Requests
Client Error
The user has sent too many requests in a given time (rate limiting).Common questions about the HTTP Status Code Lookup
What is the difference between 401 and 403?
401 Unauthorized means the server does not know who you are: credentials are missing or invalid, so logging in may help. 403 Forbidden means it knows who you are but you are not allowed to access the resource.
Should I use 301 or 308 for a permanent redirect?
Both are permanent and both pass SEO signals. 308 guarantees the method and body stay the same, which matters for POST requests to an API. For ordinary page moves, 301 is the common choice.
When should an API return 422 instead of 400?
Use 400 when the request cannot be parsed at all, such as broken JSON. Use 422 when it parses but the values fail validation, for example an end date before the start date.
What causes a 502 or 504 error?
Both come from a proxy or gateway, such as a load balancer or a CDN, in front of the real server. 502 means the upstream server sent an invalid response or refused the connection; 504 means it did not answer in time.
Is this tool free?
Yes, it's free to use. No signup, no email required. Get results on this page.
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