Tool category

Web & URL Tools

When a request misbehaves, the first clues are usually the status code and the client that sent it. These references and parsers help you interpret what a server returned and which browser or device made the request.

HTTP Status Codes

Look up common HTTP status codes by number or meaning.

User-Agent Parser

Parse a user-agent string into browser, engine, OS, and device details.

Reading status codes

The first digit tells you the class: 2xx success, 3xx redirect, 4xx a problem with the request, 5xx a problem on the server. Knowing the difference between 401 and 403, or 502 and 504, points you to the right layer to debug.

User agents as hints

User-agent strings identify the browser and operating system, but they can be changed by the client and are gradually being reduced by browsers. Use them for debugging and analytics, not for security decisions.