Open CRT Online

Read an SSL/TLS certificate (.crt, .cer, .pem) and see its owner, issuer and expiry date.

Drop a file here

or

Your file stays on your device.

  • Preview: Good
  • File info: Yes
  • Search: No
  • Editing: No

About CRT files

Certificate files prove the identity of a website, server, company or person. They come as .crt, .cer or .pem files, either as text (PEM) or in binary form (DER), and follow the X.509 standard.

Open Online reads the certificate in your browser: subject and issuer, validity dates, alternative names, key type and size, key usage, and the SHA-256 and SHA-1 fingerprints. A PEM file with several certificates, such as a chain, shows each of them. Nothing is uploaded.

What you can do here

  • See who the certificate was issued to and by
  • Check the validity dates and how long it is still valid
  • Read alternative names, key usage and key type
  • Compare SHA-256 and SHA-1 fingerprints
  • Browse every certificate in a PEM bundle

Limitations

  • The signature and the chain of trust are not verified.
  • Private keys and certificate requests in the same file are never shown.

Privacy

The file is read by your browser and stays on your device. Open Online has no server that could receive it, and nothing is stored once you close the tab. Privacy policy

Common questions

Is it safe to open a certificate here?

Yes. Certificates are public documents, and the file is read only on your device. Private keys in the same file are detected but never displayed.

Does Open Online check that the certificate is trusted?

No. It reads the contents and compares the dates with today, but does not verify the signature or the chain of trust.

How do I compare fingerprints?

The SHA-256 and SHA-1 fingerprints are shown in the same format as browsers and OpenSSL use, so you can compare them directly.