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All categories →Most looked-up errors
688 errors documentedHTTP 403 Forbidden
The server understood the request but refuses to authorize it — you (or the server process) are not allowed to access this resour…
HTTP 404 Not Found
The server can’t find anything at the requested URL.
HTTP 200 OK (but something is still wrong)
The request succeeded at the HTTP level — yet the page is blank, the data is wrong, or an error is hidden inside the response bod…
The application was unable to start correctly (0xc000007b)
A program loaded a DLL of the wrong architecture (32-bit vs 64-bit) or a corrupted runtime library.
fatal: unable to access 'https://…': SSL certificate problem: unable to get local issuer certificate
Git doesn’t trust the HTTPS server’s certificate — corporate proxy, self-hosted Git with an internal CA, or outdated CA bundle.
MySQL ERROR 1045 (28000): Access denied for user
MySQL rejected the login — wrong password, wrong user/host combination, or the user doesn’t exist.
HTTP 400 Bad Request
The server could not understand the request because its syntax, headers or body are malformed or invalid.
java.lang.ClassNotFoundException / NoClassDefFoundError
The JVM couldn’t find a class on the classpath at runtime.
Cloudflare Error 522: Connection Timed Out
Cloudflare’s TCP connection to your origin timed out — the origin didn’t answer at all.
URIError: URI malformed
decodeURIComponent/decodeURI received an invalid percent-encoded sequence.
django.core.exceptions.DisallowedHost: Invalid HTTP_HOST header: 'x'. You may need to add 'x' to ALLOWED_HOSTS.
The request’s Host header isn’t listed in Django’s ALLOWED_HOSTS.
System.NullReferenceException: Object reference not set to an instance of an object
Code dereferenced a variable that is `null` — the .NET equivalent of Java’s NullPointerException.
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Paste a raw error, log line, HTTP response or stack trace. We detect the error code, platform and request, match it against our knowledge base, and tell you the likely cause and what to check first.
403 Forbidden nginx/1.24.0 GET /api/usersAnalyze an error
⚖️ Confusing pairs, explained
- 404 vs 410: Not Found vs Gone
- 301 vs 302: Permanent vs Temporary Redirect
- 401 vs 403: Unauthorized vs Forbidden
- 406 vs 415: Not Acceptable vs Unsupported Media Type
- 412 vs 428: Precondition Failed vs Precondition Required
- 400 vs 422: Bad Request vs Unprocessable Content