HTTP status code reference with likely causes and where to look

Break a URL into its components and query parameters

MIME type and file extension reference

Parse a User-Agent string into browser and OS details

CIDR subnet calculator with membership checks

Inspect response headers and security header coverage

DNS record lookup across 8 record types

See your public IP and look up registration data for any IP

SSL certificate checker: expiry, chain, and TLS version

Generate Open Graph and Twitter Card tags

Generate robots.txt, including AI crawler rules

Convert between JWK and PEM public keys

Connect to and debug WebSocket endpoints online

Analyze HAR files to find slow requests and large assets

Paste an SSE stream and rebuild the reply, reasoning, and tool calls

Common port reference with exposure risk warnings