HTTP Status Codes: Tips and Common Mistakes

The most common HTTP status code mistakes are returning 200 for failures, confusing 401 with 403, and using the wrong redirect code — each one misleads clients and search engines. Choosing the correct code is a small decision that pays off in cleaner logs, correct caching and fewer support tickets.

This guide gathers best practices for choosing codes and the pitfalls that trip up API and web teams. Keep the HTTP Status Code Lookup open beside your editor to confirm the exact meaning before you ship.

Best practices for choosing a code

• Let the class carry the message. Return 2xx only for genuine success, 4xx when the caller must fix the request, and 5xx when your server failed — never blur these.
• Never return 200 with an error body. Clients and monitoring tools trust the status line; a 200 that hides a failure defeats retries, alerting and caching.
• Pick the specific code, not just the class. 422 for validation errors is more useful than a blanket 400, and 404 versus 410 tells crawlers whether a page is gone for good.
• Include Retry-After with 429 and 503 so clients back off politely instead of hammering you.
• Match redirects to intent. 301 for permanent moves, 302 or 307 for temporary ones.

Common mistakes and their fixes

The 301-vs-302 and 401-vs-403 traps

Two confusions cause most of the damage. First, 301 versus 302: a 301 tells search engines the resource has permanently moved and rank should follow the new URL, while a 302 says "temporary, keep using the old address." Using 302 for a real move quietly costs you SEO. Second, 401 versus 403: 401 Unauthorized means the server does not know who you are, so authentication is missing or failed; 403 Forbidden means it knows exactly who you are and is refusing anyway. Returning 401 for a permission problem sends clients into a useless re-login loop.

Troubleshooting 5xx errors

When you see a 5xx, read the specific code before touching code. A 502 Bad Gateway and 504 Gateway Timeout point upstream — a failing or slow backend behind a proxy — whereas 500 Internal Server Error is a fault in your own application. 503 Service Unavailable usually means overload or maintenance and should carry a Retry-After. Confirming the exact meaning in the lookup narrows where to look before you start reading stack traces.

Try the HTTP Status Code Lookup — free and 100% in your browser.

FAQ

When should I use 422 instead of 400?

Use 400 when the request itself is malformed and use 422 when the syntax is fine but the data fails validation rules. Splitting them makes client-side error handling far cleaner.

Is it wrong to return 404 for a resource the user cannot access?

Not always — some APIs deliberately return 404 instead of 403 to avoid revealing that a resource exists. It is a valid privacy trade-off, but be consistent about which you choose.

Which code should a rate limiter return?

429 Too Many Requests, ideally with a Retry-After header telling the client how long to wait before trying again.

Do redirect codes affect caching?

Yes. A 301 is cacheable and can be stored aggressively by browsers and proxies, so use it only when the move is truly permanent; a 302 is treated as temporary and not cached the same way.

Related free tools

• MIME Type Lookup — set the right Content-Type on responses
• User Agent Parser — inspect client strings in your logs
• URL Parser — verify redirect targets and query strings
• JSON Formatter — read error response bodies at a glance

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