HTTP Status Codes Every API Developer Should Know

HTTP status codes are an important part of API communication.

They tell clients whether a request succeeded, failed, or requires additional action.

2xx Success

Common codes include:

200 OK: Request completed successfully.

201 Created: A resource was successfully created.

204 No Content: Request succeeded without a response body.

4xx Client Errors

400 Bad Request: Request contains invalid input.

401 Unauthorized: Authentication is missing or invalid.

403 Forbidden: The caller is not permitted to access the resource.

404 Not Found: Requested resource does not exist.

429 Too Many Requests: Client exceeded an applicable traffic limit.

5xx Server Errors

500 Internal Server Error: General server-side failure.

502 Bad Gateway: Gateway received an invalid response from an upstream service.

503 Service Unavailable: Service is temporarily unavailable.

504 Gateway Timeout: Upstream service did not respond within the expected time.

Why Status Codes Matter

Correct status codes help API consumers handle failures properly and help monitoring systems identify problems.

Conclusion

HTTP status codes are part of the API contract.

Using them consistently improves developer experience, troubleshooting, and API reliability.