Paste a certificate and read what is actually inside it - subject, issuer, dates, key details and every name it covers.

Include the BEGIN and END lines. Nothing you paste is stored.
Working

Useful when

  • You have several .crt files and need to know which is the leaf and which are intermediates
  • A certificate arrived and you want to confirm the names before installing it
  • You are checking an expiry date without waiting for a browser to complain
  • You need the exact issuer name to find the right intermediate bundle

Telling a leaf from an intermediate

Download a certificate and you often get several files with unhelpful names. Decode each one: the leaf has your domain as its subject, an intermediate has the authority's name as its subject and a different authority as its issuer, and a root has the same name in both. Install them in the wrong order and browsers report an incomplete chain.

Reading it without a server

This works on any certificate file, whether or not it is installed anywhere. That makes it the quick way to check a certificate you have been sent, or one you pulled out of a backup, before going anywhere near a live server.