What HTTP status codes does this tool cover?

HTTP Status Debugger covers all standard HTTP status codes across 1xx (Informational), 2xx (Success), 3xx (Redirection), 4xx (Client Error), and 5xx (Server Error) categories — including commonly encountered codes like 400, 401, 403, 404, 409, 422, 429, 500, 502, 503, and 504.

How does the system layer identification work?

Each HTTP status code is mapped to the system layer most likely responsible for the error — such as Client, Authentication, Authorization, API Gateway, Reverse Proxy, Application Server, Database, or Infrastructure. This helps you quickly narrow down where to start debugging.

Is my data sent to any server?

The Code Lookup tab runs entirely in your browser — no data is sent anywhere. The URL Tester sends requests through a server-side proxy to avoid CORS restrictions, but no request data is stored or logged.

Can I search by error name or keyword instead of code?

Yes! You can search by keyword (e.g., 'timeout', 'gateway', 'auth') to find relevant status codes. The search matches against code names, system layers, and common causes.

What's the difference between 401 Unauthorized and 403 Forbidden?

401 Unauthorized means the request lacks valid authentication credentials — the server doesn't know who you are. 403 Forbidden means the server knows who you are but you don't have permission to access the resource. Fix 401 by providing valid credentials; fix 403 by requesting appropriate permissions.

What causes 502 Bad Gateway and how do I fix it?

502 Bad Gateway means a gateway or reverse proxy received an invalid response from an upstream server. Common causes include the upstream service being down, network issues, or malformed responses. Debug by checking upstream service health, proxy logs, and network connectivity.

How does the URL Tester work?

The URL Tester lets you send real HTTP requests to any public URL — similar to Postman. You can choose the HTTP method (GET, POST, PUT, DELETE, etc.), add custom headers, set authorization (Bearer, Basic, API Key), and include a request body. The tool shows the response status, headers, body (with JSON formatting), and any redirect chain, plus auto-displays debug guidance for the returned status code.

Can I test APIs that require authentication?

Yes! The URL Tester supports Bearer token, Basic auth (username/password), and API Key authentication. Select the auth type, enter your credentials, and they'll be included in the request headers automatically.

Developer Tool

Decode HTTP Errors
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Look up any HTTP status code or test real URLs with custom headers, auth, and body — like a lightweight Postman. See causes, system layers, debug checklists, and fixes instantly.

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Instant Lookup

Enter any HTTP status code and get a detailed breakdown of causes, layers, and fixes in milliseconds.

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URL Tester

Test real URLs with custom methods, headers, auth, and body — like a lightweight Postman right in your browser.

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Debug Checklists

Get actionable debug steps, response headers, redirect chains, and typical fixes for any HTTP error.

Frequently Asked Questions

Everything you need to know about HTTP Status Debugger.

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Instant Lookup

URL Tester

Debug Checklists

Frequently Asked Questions

Decode HTTP Errors
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