TLS and domain
SSL certificate checker
Check a certificate issuer, validity dates and days to expiry.
What this checks
An SSL certificate proves a site is who it says it is and encrypts traffic to it. Every certificate has an issuer and a fixed validity window, after which browsers show a warning.
This checker reads the most recent certificate for a domain from public Certificate Transparency logs and shows the issuer, the valid-from and valid-to dates and how many days are left.
Why it matters
An expired certificate breaks the padlock and throws a full-page browser warning that scares visitors off. It is one of the most common and most avoidable ways a site looks broken.
Certificates renew on a cycle, often every 90 days with Let us Encrypt, so an unwatched renewal that fails is easy to miss until a client calls.
How to fix common failures
Renew before it expires
Set the renewal to run well before the valid-to date, and confirm it actually completed.
Automate renewal
Use automated issuance (ACME, your host or CDN) so a human does not have to remember.
Check the whole chain
A missing intermediate certificate can fail on some devices even when it looks fine in your browser.
SSL certificate checker is one check. Janitor watches SSL validity and expiry automatically across every client site and puts it in a branded report.
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Related
FAQ
SSL certificate checker FAQ
How does this checker read the certificate?
It reads the most recently issued certificate for the domain from public Certificate Transparency logs, which is a close proxy for the live certificate. For the exact serving certificate and the full chain, a direct TLS check is best, and Janitor does this on a schedule.
How often should I check SSL?
Continuously, ideally with a warning 30 days out. A one-off check tells you about today; monitoring tells you before the next renewal fails.
What if no certificate is found?
The site may be new, may not use HTTPS, or its certificates may not appear in the public logs the tool reads. Confirm the site loads over https first.
Get started
Check it once, or watch it for every client
Janitor runs around two dozen checks on every site you manage and turns them into a branded report.
30-day free trial. No credit card required.