When does this certificate expire — and will the chain hold?

Paste a hostname. Certprobe opens a real TLS connection to the server, reads the certificate chain it actually presents, and reports — in plain language — the expiry date, the issuer, every hostname the certificate covers, and whether the chain the server sends is complete enough for every browser.

Probe a certificate → See plans

What this tool checks

Expiry date — exact date and days remaining. Reports expired, expiring soon (<30 days), or healthy.
Chain completeness — did the server send its intermediate certificates? Desktop browsers may paper over a missing intermediate; mobile browsers will reject it.
Subject & issuer — who issued the certificate and what entity it was issued to, exactly as the server presents them.
Subject Alternative Names — every hostname the certificate covers. Check whether a hostname is actually listed.
Serial number & fingerprint — for cross-referencing against revocation lists or CA records.

Why the chain matters

A certificate can be unexpired and your site can still be broken. The most common failure mode: the server sends the leaf certificate but omits the intermediate CA certificate. Desktop browsers have a cache of common intermediates and may paper over the gap. Mobile browsers do not — they reject the connection.

Certprobe tells you what the server actually sends, not what a browser might synthesise. If the intermediate is missing, it says so.

What this tool does not do

No alerts or reminders. Certprobe answers when you ask it. There are no email reminders, scheduled checks, or push notifications — and if those are important to you, the pricing page tracks when they become available.

No range scanning. Certprobe checks one hostname at a time — exactly the one you type. It does not enumerate subdomains, scan IP ranges, or probe adjacent services.

Platform limitation you should know

Certprobe runs on Cloudflare Workers. A Cloudflare Worker cannot open a direct TCP connection to a host that is itself behind Cloudflare's proxy. If you probe a proxied Cloudflare host, Certprobe will report it as unreachable — this is a platform limitation, not a finding about your server.