When does this certificate expire, and what breaks when it does?
Paste a hostname. Tlscheck opens a TLS connection, reads the certificate chain the server actually presents, and reports the expiry date, issuer, every hostname the certificate covers, and whether the chain the server sends is complete.
The tool answers when you ask it. No alerts, no reminders, no scheduled re-checks. One hostname at a time.
The point is the chain, not just the date
A certificate can be valid and the site still break, because the server sends the leaf without its intermediate. Browsers on desktop paper over it from cache. Mobile clients do not. That failure is invisible to anyone looking only at the expiry date.
1
Connect
Tlscheck opens a TLS connection to the hostname you supply on port 443 and reads whatever certificate chain the server presents during the handshake.
2
Parse
Every certificate in the chain is parsed inline — no external services, no API keys. Expiry date, issuer name, serial number, and all Subject Alternative Names are extracted from the raw DER data.
3
Report
The result is a structured report: the validity status, days remaining, issuer chain, SAN list, and a clear statement of whether the chain is complete. If a field is absent on the server, the report says absent — no values are inferred.
What the report shows
Expiry date and days remaining
Colour-coded: green for valid, amber when expiring in under 30 days, red when expired or under 7 days.
Issuer and subject
The exact Distinguished Names — who issued the certificate and which entity it was issued to — parsed directly from the DER encoding.
All SANs listed
Every hostname the certificate is valid for, extracted from the subjectAltName extension. No summarising — the full list is shown.
Chain completeness check
The server may send only the leaf certificate. Tlscheck checks whether every certificate in the chain links to the next, and whether the chain reaches a trusted root.
Cloudflare edge detection
If the certificate presented belongs to Cloudflare rather than the origin server, the report says so. Hosts behind Cloudflare cannot be reached through this tool — a known platform limitation.
No sign-up. No data stored. One hostname at a time.
This tool tells you what a server is actually presenting over the wire. No accounts, no saved history, no email — just an answer when you need one.
Inspect a hostname now