SSL/TLS certificate checker
Check any site's certificate: expiry, issuer, hostname match and chain of trust. Free, no signup.
Never get caught by an expired certificate
WWT checks your certificate, TLS version, uptime, domain expiry and email security every day and warns you well before anything breaks. Free, no credit card.
How to read your SSL/TLS result
Every result starts with the certificate's subject and issuer: who it was issued to, and which certificate authority signed it. The 'valid to' date matters most - once it passes, browsers show a full-page security warning and most visitors leave at once. WWT turns the remaining days red as expiry approaches.
The tool also reports the negotiated TLS version and the full chain of trust, from the leaf certificate up to the root. A chain missing an intermediate certificate often works in one browser and fails in another - exactly the silent problem that continuous monitoring is built to catch before your visitors do.
Certificate lifetimes are getting shorter
The CA/Browser Forum approved ballot SC-081v3, which cuts the maximum lifetime of a public TLS certificate in three steps. A certificate issued on or after each date below cannot be valid for longer than the number of days shown.
- 2026-03-15Maximum certificate lifetime drops to 200 days
- 2027-03-15Maximum certificate lifetime drops to 100 days
- 2029-03-15Maximum certificate lifetime drops to 47 days
Each cut multiplies the number of chances to miss a renewal. An annual calendar reminder was workable at 398 days; at 47 it is not. That is why automated issuance, plus an independent check on the certificate your server actually serves, is becoming standard practice rather than a nice-to-have.
About SSL/TLS certificates
What is an SSL/TLS certificate?
An SSL/TLS certificate proves a website's identity and encrypts traffic between the browser and the server. Without a valid one, browsers show a security warning.
Why does certificate expiry matter?
When a certificate expires, every visitor gets a security warning and HTTPS breaks - often on a weekend or holiday. Renewing in time avoids outages and lost trust.
Which TLS versions are safe?
Modern best practice is TLS 1.2 and 1.3 only. TLS 1.0 and 1.1 are deprecated and considered insecure.
Why does my browser say NET::ERR_CERT_DATE_INVALID?
That error means the certificate is outside its validity window, almost always because it expired. Check the expiry date above: if it is in the past, renew the certificate and reinstall it. If the date looks fine, the visitor's own device clock is wrong, which produces the same message.
Why does a certificate work in one browser but fail in another?
Usually an incomplete chain: the server sends the leaf certificate but omits an intermediate one. Browsers that cached that intermediate succeed, a fresh device fails. The chain view shows whether every link is present.