About ssl certificate checker
An SSL/TLS certificate lets a site use HTTPS. The checker shows who issued it, which names it covers and when it expires.
What to look for
- The expiry date. An expired certificate shows a browser warning and can cost visitors.
- That the certificate covers your domain and the www version.
- The issuing authority and the certificate chain.
Automate renewal
Free certificates from Let's Encrypt last 90 days, so set up automatic renewal and a monitor for expiry.
A worked example
A check of a site shows a certificate issued by Let's Encrypt for example.com and www.example.com, valid for 90 days and expiring in 23 days. That is a warning to check that automatic renewal is working, before visitors see an error.
Common certificate errors
- Expired certificate.
- Name mismatch, when the certificate does not list the domain visitors use.
- Missing intermediate certificate, which breaks some devices.
Fixing a problem
If the name does not match, request a new certificate that lists every host name you use. If the chain is incomplete, install the intermediate certificate that your authority provides.
