API Error Code Decoder
Decode HTTP status codes and OAuth 2.0 error strings with plain-English descriptions, common causes, and actionable fix suggestions. Covers every HTTP 1xx–5xx status code and all standard OAuth 2.0 error responses. Results appear instantly as you type.
How to Use API Error Code Decoder
How to Use the API Error Code Decoder
Step 1: Type a Code or Error String
Type any HTTP status code (e.g., 404, 429, 503) or OAuth 2.0 error string (e.g., invalid_grant, access_denied) into the search box. Results appear instantly as you type.
Step 2: Use Quick Examples
Click any of the quick-pick buttons below the search box to instantly decode common codes:
- 400 — Bad Request (malformed payload)
- 401 — Unauthorized (missing or invalid token)
- 403 — Forbidden (no permission)
- 404 — Not Found
- 429 — Too Many Requests (rate limited)
- 500 — Internal Server Error
- 503 — Service Unavailable
- invalid_grant — OAuth refresh token or auth code problem
Step 3: Read the Decoded Result
For an exact match, you will see:
- Code and name — the HTTP status code or OAuth error identifier and its official name
- Category badge — color-coded by type (4xx Client Error, 5xx Server Error, OAuth 2.0, etc.)
- Description — a plain-English explanation of what the code means
- Common Causes — the most frequent reasons this error occurs in production
- How to Fix — concrete, actionable steps to diagnose and resolve the error
If you type a partial code (e.g., 40 or 5), a list of matching codes appears — click any entry to see its full details.
Supported Error Codes
HTTP Status Codes — All major 1xx, 2xx, 3xx, 4xx, and 5xx codes including 100, 101, 200, 201, 204, 206, 301, 302, 304, 307, 308, 400, 401, 403, 404, 405, 408, 409, 410, 413, 415, 422, 429, 500, 501, 502, 503, 504
OAuth 2.0 Errors — All RFC 6749 standard error codes: invalid_request, invalid_client, invalid_grant, unauthorized_client, unsupported_grant_type, invalid_scope, access_denied, token_expired, invalid_token, insufficient_scope, server_error, temporarily_unavailable
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