What File Extension Is Used for SSL Certificates?

SSL certificates can use several file extensions depending on the format and purpose of the file. Below are the common file extensions used for SSL certificates:

1. .crt or .cer

• These extensions are used for the certificate itself, typically in X.509 format.
• They store the public key and certificate details.

2. .key

• This extension is used for the private key, which must be kept secure and never shared.

3. .pem

• A commonly used extension for SSL certificates and keys in Base64-encoded format.
• It may contain:
  • The certificate (—–BEGIN CERTIFICATE—–)
  • The private key (—–BEGIN PRIVATE KEY—–)
  • Intermediate certificates.

4. .pfx or .p12

• These are PKCS#12 files that bundle the certificate, private key, and intermediate certificates into one file.
• Often used in Windows-based environments.

5. .csr

• This is the Certificate Signing Request file, which is generated during the SSL setup process and used to request an SSL certificate.