HTTP Status Codes Reference
Every HTTP status code, searchable · what each means, when to use it, and which ones have security implications worth knowing.
Frequently asked
401 or 403 · which one do I return?
401 Unauthorized means "you haven't authenticated" (send credentials and retry). 403 Forbidden means "I know who you are, and no". Returning 404 instead of 403 for private resources is a legitimate pattern to avoid confirming they exist.
Do status codes affect SEO?
Directly: 301 passes link equity on moves, 302 signals temporary, 404/410 drop pages from the index, and soft-404s (a 200 that says "not found") waste crawl budget. Server errors (5xx) sustained over days can deindex pages.
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