.pem

What is a .pem file?

PEM is the most common format for SSL/TLS certificates and keys — Base64-encoded data between header/footer lines.

Use caution
Type Security
By IETF (Privacy-Enhanced Mail, RFC 7468)
MIME application/x-pem-file

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What is it

PEM is the format that keeps HTTPS working. Every SSL certificate, every TLS private key, every certificate chain you've configured on a web server was probably in PEM format. The structure is simple: Base64-encoded binary data between `-----BEGIN CERTIFICATE-----` and `-----END CERTIFICATE-----` markers (or BEGIN PRIVATE KEY, BEGIN RSA PRIVATE KEY, etc.).

The format's beauty is its text nature. PEM files can be concatenated (stack a certificate and its chain in one file), emailed, pasted into web forms, stored in environment variables, and version-controlled. The Base64 encoding makes binary cryptographic data safe for text-only transport channels.

A PEM file can contain a certificate, a private key, a certificate chain, a CSR, or multiple items concatenated. The BEGIN/END markers tell you what's inside. Handle private key PEM files like passwords — if someone gets your private key, they can impersonate your server. Certificate PEM files are public and safe to share.

Technical details
Full Name
PEM Certificate/Key File
MIME Type
application/x-pem-file
Developer
IETF (Privacy-Enhanced Mail, RFC 7468)
Magic Bytes
N/A
Safety
.pem requires caution. PEM files containing private keys should be kept secret. Certificate-only PEM files are safe to share.
What opens it
openssl (CLI)
FREE Windows / Mac / Linux
Any text editor
FREE Windows / Mac / Linux
KeyStore Explorer
FREE Windows / Mac / Linux
FAQ
How do I view the contents of a PEM file?
For certificates: `openssl x509 -in cert.pem -text -noout`. For private keys: `openssl rsa -in key.pem -text -noout`. Or open in any text editor to see the Base64 data and identify the type from the BEGIN/END markers.
Is it safe to share a PEM file?
It depends on what's inside. Certificate PEM files (BEGIN CERTIFICATE) are public and safe to share. Private key PEM files (BEGIN PRIVATE KEY) must be kept secret — sharing them compromises your security.
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