Developer Reference

Some values you look up again and again without ever memorizing them. For example: whether 302 or 307 is the redirect that preserves the request method, the MIME type for a woff2 font, or what 644 means when a deploy fails with a permission error.

These pages are lookups, not tutorials. The HTTP status reference lists every code with what it means and when to send it, and filters as you type. The MIME type lookup works in both directions, from extension to type and back. The chmod calculator turns checkboxes into the octal number, and the octal number back into rwxr-xr-x. The user agent parser breaks a UA string into browser, engine, operating system and device, and can read your own.

Every page is static data or client-side parsing, so it loads quickly and keeps working offline once it has loaded.