What is an HTTP status code?
HTTP status codes are three-digit response codes returned by a server to show what happened to a request. You will see them in browser developer tools, API responses, server logs, uptime checks, and reverse proxy dashboards.
Understanding status code categories
- 1xx informational: The server received the request and the exchange is still in progress.
- 2xx success: The request completed successfully.
- 3xx redirection: The client needs to follow another location or reuse a cached result.
- 4xx client error: The request itself has a problem, such as a missing resource, invalid input, or failed authentication.
- 5xx server error: The server or an upstream dependency failed while handling a valid request.
When to use this lookup
Use this lookup when you need to confirm what a status code means, compare similar codes such as 401 vs 403 or 502 vs 504, or search by a phrase from an error message. The tool supports searching by code, status name, and localized description.
Why correct interpretation matters
A status code is often the fastest clue during debugging. A 4xx response usually points to the request, credentials, or target resource, while a 5xx response usually points to the application, gateway, or upstream service. Reading the category first helps you choose the right next step.