Cert Counter от 8kbetviet

CertCounter is an efficient Firefox extension that helps you count down to certificate expiration. It tracks the number of days left until website certificates expire and displays the count on a padlock icon in the toolbar for easy reference.

When there are less than 29 days remaining, the icon turns red, signaling a need for prompt action. Additionally, if the site connection is not encrypted, it shows an unlocked red padlock, raising security concerns.