SSL certificate decoder (PEM and CSR)
Paste an SSL certificate in PEM format or a CSR and see the domain, issuer, validity, alternative names, key and fingerprints.
How to useDecode the certificate.
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SSL certificate decoder (PEM and CSR): what it is for
Paste a PEM certificate or open a .crt, .cer, .pem or .csr file and see the subject, issuer, validity dates with a bar showing days left, serial number, key type and size, signature algorithm, alternative names (SAN) and SHA-256 and SHA-1 fingerprints. Self-signed certificates get a warning.
Everything runs in your browser: nothing you paste or open is sent to a server.
How to use
- Paste the certificate or open the file.
- Check domain, issuer and validity.
- Copy the fingerprints if needed.
When to use it
- Check a certificate before installing it.
- See when the SSL expires.
- Review a CSR before sending it to the CA.
Frequently asked questions
What is a PEM file?
It is the most common text format for certificates and keys: the binary content in Base64 between the -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- lines. .crt, .cer and .pem files are usually in this format.
And the CSR?
The CSR (Certificate Signing Request) is the request you generate on the server and send to the certificate authority. It contains the domain, company details and public key, but no issuer or validity yet.
Can I paste the private key?
Don’t. The tool only needs the certificate or CSR, which are public. Reading happens in your browser, nothing is sent to a server.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 are free.