Networking · Diagnostics

OSI Connection Probe

Punch in a website and this probes it layer by layer — resolving DNS, opening a connection, checking the TLS handshake and the HTTP response — then builds an OSI scorecard showing which layers are confirmed working and which need a closer look. Layers 1, 2, and 5 can't be seen from outside, so for those it hands you a checklist for your own side.

→ OSI Model Reference → Security Headers Analyzer → Certificate Decoder

Probes are read-only: a DNS lookup and a single HTTP request. Nothing is stored.

No probe run yet. Enter a website above to build its OSI scorecard.

How this works & what it can't see: DNS resolution uses DNS-over-HTTPS (Cloudflare, with Google as a fallback). The HTTP request goes through a stateless Cloudflare Worker so it can reach cross-origin sites the browser's CORS rules would block; if the Worker is unavailable the tool falls back to a best-effort browser check. Layers 1 (Physical), 2 (Data Link), and 5 (Session) are local to each network segment and can't be probed from here — those cards give you checks for your own side instead. Nothing you probe is logged or stored.