Dev Reference

Parse a Cache-Control value, explain each directive, compute freshness and flag conflicts or leaks.

Parse a Content-Security-Policy header value, explain each directive and flag risky settings like unsafe-inline.

Convert a timestamp (RFC 3339, ISO 8601, HTTP-date or epoch seconds) to RFC 3339, HTTP-date, RFC 5322, basic ISO and epoch.

Validate an ISO 8601 or RFC 3339 date, time, timestamp, duration or interval, and say which standard it satisfies.

DNS record type lookup by name (MX) or number (15): IANA meaning, RFC reference and typical use.

Explain an HTTP header: request or response, purpose, security notes, and its IANA registration status.

Whether an HTTP method is safe and idempotent (IANA registry), what it is for, and request-body semantics.

All registered HTTP status codes in a class (1xx to 5xx) with names and one-line meanings.

HTTP status code meaning, typical cause, client action and cacheability, from the IANA registry and RFC 9110.

Media type (MIME) for a file extension, or extensions for a media type, with IANA registration status.

IANA service name and common use for a TCP/UDP port (about 130 well-known ports), plus the port range class.

Unicode character lookup by code point or character: name, block, category, UTF-8/UTF-16 bytes and HTML/JS/CSS escapes.