Quick answer: Status codes are compact signals from a web server. For link diagnosis, a small set appears repeatedly and quickly explains what happened to a request.
2xx: the request succeeded
200 OK is the usual successful page response. Other 2xx codes exist, especially in APIs, but 200 is the one most people encounter when checking a normal webpage.
3xx: go somewhere else
301, 302, 303, 307 and 308 tell the client to use another location. Redirects are not errors, but long chains add work and can hide an unexpected final destination.
404 versus 410
404 means the resource was not found. 410 Gone is a stronger statement that the resource is intentionally no longer available. In practice many sites use 404 for both situations.
429: too many requests
429 indicates rate limiting. A monitoring tool or crawler that sees 429 should back off rather than treating the page as permanently dead.
5xx: server-side problems
500 and related codes mean the server could not complete the request. Temporary outages can resolve later, so monitoring across time is often more informative than one isolated check.
Use the tools
For a live URL, URL Checkup combines redirect tracing, metadata, tracking detection and health scoring. If the link is already broken, Smart URL Recovery can search the same site for likely replacement pages. For long-lived public links or printed QR codes, Rescue Link adds a stable managed destination.
Important limitation
URLClinic provides technical information and workflow tools. It does not certify the identity, safety, legality or accuracy of third-party websites. Verify important destinations independently.