HTTP Status Code Lookup — HTTP Status Codes Reference
Look up any HTTP status code with description and common use cases.
Reviewed by the ToolNestr Editorial Team — July 2026
How HTTP status codes work
HTTP status codes are three-digit numbers returned by a server in response to a client's request. They indicate the result of the HTTP transaction — whether it succeeded, failed, or needs further action. Every web developer, system administrator, and API designer encounters them daily.
When a client (browser, API consumer, or tool like cURL) sends an HTTP request, the server processes it and returns a response. The first line of the response includes the HTTP version, the status code, and a reason phrase. The status code is the key piece of information — it tells the client what happened in a machine-readable way.
Status code classes
HTTP status codes are grouped into five classes, identified by the first digit. Memorizing these five categories helps you narrow down any issue immediately.
1xx
Informational
Request received, continuing.
2xx
Success
Request received and accepted.
3xx
Redirection
Further action needed.
4xx
Client Error
Request has bad syntax.
5xx
Server Error
Server failed to fulfill.
Most important status codes
While there are many standard status codes, these 13 codes account for the vast majority of what you will encounter in practice:
Standard success response.
Resource created (POST/PUT).
Success, no body (DELETE).
Resource has new URL.
Temporary redirect.
Use cached version.
Malformed request syntax.
Authentication required.
No permission, even with auth.
Resource does not exist.
Generic server failure.
Upstream server invalid.
Server overloaded or down.
Use cases
API Debugging
When an API call fails, the status code is the first clue. 400 means fix the request. 401/403 means fix the auth. 5xx means the server is the problem.
Server Troubleshooting
Monitoring tools report status codes. A surge in 5xx responses signals an outage. A spike in 429s indicates rate limiting is being hit.
Learning HTTP
Understanding status codes is fundamental to web development. They appear in browser dev tools, server logs, and every HTTP library.
Tips for using HTTP status codes
Memorize the five classes
The first digit of any status code tells you its category. When you see 4xx, you know the client made a mistake. 5xx means the server is failing. This narrows down the debugging process immediately.
Don't confuse 401 and 403
401 Unauthorized means "provide credentials" (you haven't authenticated). 403 Forbidden means "your credentials don't have access" (you're authenticated but not authorized).
Watch for redirect loops
3xx codes cause browsers to follow the Location header. If A redirects to B which redirects back to A, you get a redirect loop. Browser dev tools show this clearly in the Network tab.
Rate limiting (429) is becoming common
Many APIs return 429 Too Many Requests when you exceed their rate limit. Check the Retry-After header to see when you can retry. Implement exponential backoff in your clients.
Related tools
Frequently asked questions
How many status codes are there?
Over 60 standard codes across 5 classes (1xx–5xx).
What is the most common status code?
200 OK (success) and 404 Not Found (resource missing) are the most common.
What is 418?
418 I'm a Teapot — an April Fools' joke from the HTCPCP protocol.
Why does 429 matter?
429 Too Many Requests — indicates rate limiting, important for API clients.