Developer references & cheat sheets
Some lookups happen too often to search for each time: what an HTTP status code implies about the response shape, which ARIA role and attributes an accessible component needs, what a Linux exit code or errno number actually means, or which port a protocol uses by default. These pages collect that reference material in one searchable index instead of you re-finding the same specification page every time.
The web-facing references cover HTTP status codes with response shapes, HTTP methods, headers and MIME types in one index, ARIA roles with implementation examples, and JWT claims and OAuth error codes. Character reference and Developer cheat sheets round out day-to-day lookups with ASCII, Unicode and HTML entities, plus Git, regex and cron syntax. The systems references cover lower-level lookups: Linux exit codes, signals, errno and syscall numbers, network ports, and IANA time zones, locales and AWS region codes.
9 tools
HTTP and web standards
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HTTP status codes
Look up HTTP status codes with response shapes and first checks
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HTTP methods, headers and MIME reference
Search HTTP methods, headers and MIME types in one curated index
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Accessibility and ARIA reference
Search ARIA roles and attributes with implementation examples
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JWT claims and OAuth errors
Look up JWT claims and OAuth error codes with response examples
Systems and network reference
Developer Reference tools FAQ
401 Unauthorized means the request lacks valid authentication credentials at all, while 403 Forbidden means the credentials were understood but don't grant access to that resource. HTTP status codes lists both with their expected response shapes and the first thing to check for each.
A JWT's header and payload are just base64url-encoded JSON, not encrypted, so you can read the claims without the signing secret; you only need the secret to verify the signature. Auth reference lists standard JWT claims and OAuth error codes with response examples for exactly this kind of lookup.
By convention, an exit code above 128 usually means the process was terminated by a signal, calculated as 128 plus the signal number, so 137 points to signal 9, SIGKILL. Linux reference lists exit codes, signals, errno and syscall numbers together for looking this up directly.