Error Code Reference

The Error Code Reference is a comprehensive, browser-based lookup tool for error codes across the most commonly encountered programming platforms and operating systems. When you hit an unfamiliar error code during development, debugging, or production incident response, this tool gives you an instant explanation, the most common causes, and actionable resolution steps -- all without leaving your browser.

The reference currently covers eight major systems: HTTP Status Codes (400, 404, 500 and others that every web developer encounters daily), POSIX errno values (ENOENT, EACCES, ECONNREFUSED and other system-level errors), Windows HRESULT codes (E_FAIL, E_ACCESSDENIED), Node.js error codes (ERR_MODULE_NOT_FOUND, EADDRINUSE), MySQL and PostgreSQL database error codes, Python exceptions (KeyError, ImportError, FileNotFoundError), and JavaScript errors (TypeError, ReferenceError, SyntaxError).

Every entry includes four fields: the error code or name, a plain-English description of what the error means, the most common causes you will encounter in real-world development, and a concrete resolution with steps you can follow immediately. Related errors are cross-referenced so you can explore similar issues within the same system.

All processing runs entirely in your browser. No data is sent to any server, and no search queries are logged. You can search by error code number, error name, or any keyword in the description. Filter by category to narrow results to a specific system. The tool is designed for fast lookup during incident response, code review, or learning.

If you are working with HTTP errors specifically, you may also find the HTTP Status Codes Reference useful for deeper per-code documentation. For debugging stack traces, try the Log Format Parser.

1. Type an error code (e.g., "404", "ENOENT", "23505") or keyword (e.g., "permission", "timeout") into the search bar.
2. Click a category badge to filter by system: HTTP, POSIX, Windows, Node.js, MySQL, PostgreSQL, Python, or JavaScript.
3. Click any error entry to expand its full description, common cause, and resolution.
4. Use the Copy button to copy the error information to your clipboard for pasting into tickets or documentation.
5. Click related errors at the bottom of an expanded entry to jump to cross-referenced errors in the same system.
6. Press Ctrl+F (or Cmd+F) for native browser search if you need to scan the visible entries quickly.