Know a certificate is expiring before your visitors do

An expired certificate takes a site down as thoroughly as a crashed server, and it is entirely predictable. The expiry date is written into the certificate itself; it only needs reading before your visitors' browsers read it for you.

InBrief reads it once a day for every monitor with an encrypted target: an https:// website, a wss:// socket, a port checked with TLS and a mail server on implicit TLS. The monitor shows how long its certificate has left, and warnings go to your team by email ahead of the expiry date, and to Slack and your webhooks if you use them.

The sweep runs daily because an expiry date cannot change between two checks a minute apart. A plain http:// address has no certificate to read, and the monitor says so instead of showing a check that never completes.