SSLWatchGuides
How to check an SSL certificate expiration date
Three quick ways to see when a website's SSL/TLS certificate expires: online checker, browser padlock and openssl.
SSL certificate chain explained (leaf, intermediate, root)
What a certificate chain is, why "incomplete chain" errors happen and how to fix them.
TLS 1.2 vs TLS 1.3: what is the difference?
TLS 1.3 is faster and safer than TLS 1.2. Here is what changed and how to check which one a site uses.
Let's Encrypt certificate expiry: why 90 days (and getting shorter)
Why Let's Encrypt certificates expire quickly, how auto-renewal works and how to monitor it.
How to check when a domain name expires
Find a domain's registration expiry date with RDAP/WHOIS and avoid losing your domain.
How to check an SSL certificate with OpenSSL (command line)
OpenSSL commands to check SSL certificate expiry, issuer, chain and TLS version from Linux, macOS or Windows.
How to check an SSL certificate on Windows (PowerShell & command line)
Check SSL certificate expiry and TLS version on Windows using PowerShell, certutil and the certificate store.
SSL certificate validity is dropping to 47 days: timeline & what to do
The CA/Browser Forum is cutting maximum SSL/TLS certificate lifetimes from 398 days to 47 days by 2029. Here is the schedule and how to prepare.
SSL certificate expired? How to fix "Your connection is not private"
What an expired SSL certificate error means for visitors and site owners, and how to fix NET::ERR_CERT_DATE_INVALID fast.