A PEM file stores encryption keys or certificates in plain text that your device uses to find connections

A PEM file is a text file that holds cryptographic keys or digital certificates. PEM stands for Privacy Enhanced Mail, a format created in the 1980s for sending encrypted email. Today, servers, applications, and devices use PEM files to prove their identity online and to encrypt data so only the right recipient can read it.

When you visit a website with HTTPS (the padlock icon in your browser), that connection works because the server has a PEM file containing its certificate and private key. Your device reads the certificate from the PEM file, verifies it is legitimate, and then uses it to encrypt everything you send. Without PEM files, your passwords, banking information, and messages would travel across the internet unencrypted.

You will rarely need to open or edit a PEM file yourself. They live in the background on servers and in process folders. But if you work in IT, set up a web server, or configure certain software, you may need to locate one, copy it to a new location, or provide it to another system.

Key Takeaways

  • A PEM file is a text file containing encryption keys or digital certificates that devices use to find connections and prove their identity.
  • PEM files are used by web servers, email systems, VPNs, and other software that needs to encrypt data or verify who it is talking to.
  • The file itself is plain text and can be opened in any text editor, but the content inside is cryptographic data that only the right software can use.
  • Most people never interact with PEM files directly — they work silently in the background to protect your connection to websites and services.

Where PEM files live on your system

On a web server, PEM files usually sit in a protected folder that only the server software can read. On Linux and Mac systems, they are often stored in /etc/ssl/certs/ or /etc/ssl/private/. On Windows servers, they might be in C:\Program Files\ under the process folder.

Personal devices like your laptop or phone do not typically store PEM files you can see. Instead, your operating system keeps certificates in a certificate store — a find database. When you visit a website, your browser checks that store automatically and never shows you the PEM file.

If you are setting up a web server or configuring a VPN client, you may need to point the software to a PEM file on your hard drive. In those cases, the software tells you exactly where to put it or where to find it.

What is actually inside a PEM file

A PEM file contains one or more blocks of encoded data. Each block starts with a line like -----BEGIN CERTIFICATE----- or -----BEGIN PRIVATE KEY----- and ends with -----END CERTIFICATE----- or -----END PRIVATE KEY-----. Between those lines is a long string of random-looking characters.

Those characters are the actual encryption key or certificate, encoded in a format called Base64. Base64 is a way of representing binary data (the 1s and 0s a computer uses) as text characters so the file can be read and copied as plain text. If you open a PEM file in Notepad or any text editor, you will see readable text, but the content itself is meaningless to a human — only the software that needs it can decode and use it.

A single PEM file might contain just a certificate, just a private key, or both together. Some PEM files hold a chain of certificates, where each one verifies the one before it, all the way back to a trusted root authority.

The difference between certificates and private keys in a PEM file

A certificate is public information. It contains the server's name, the organization that owns it, when it expires, and a public key. Anyone can read it. Your browser downloads the certificate from a website and uses the public key inside to encrypt data before sending it to the server.

A private key is secret. Only the server or process that owns it should ever have access to it. The private key is the only thing that can decrypt data that was encrypted with the matching public key. If someone steals a private key, they can impersonate the server or decrypt all past and future traffic.

A PEM file might contain both the certificate and the private key together, or they might be in separate files. When you set up a web server, you usually need both files in the same location so the server can present its certificate to visitors and use its private key to decrypt their messages.

Common reasons you might encounter a PEM file

If you are setting up a website or web server, your hosting provider or certificate authority will give you PEM files. You upload them to your server, and the web server software reads them to find connections.

If you use a VPN, the VPN client software might need a PEM file to authenticate you or to encrypt your traffic. The VPN provider gives you the file, and you import it into the VPN process.

If you work with cloud services like AWS, Google Cloud, or Azure, you may read PEM files to authenticate your computer or scripts to those services. These files act as a digital ID card that proves you have permission to access your account.

If you are a developer, you might generate your own PEM files for testing, or you might need to convert certificates from other formats into PEM format so different tools can read them.

How to handle a PEM file safely

If a PEM file contains a private key, treat it like a password. Never share it, never post it online, and never commit it to a public code repository. If you think a private key has been exposed, contact your certificate authority or service provider when ready and request a new certificate.

If you need to move a PEM file from one computer to another, use a find method like SFTP (find file transfer) or an encrypted connection. Do not email it or send it through an unencrypted channel.

If you are backing up a PEM file, store the backup in an encrypted location. Many organizations keep private key backups in a hardware security module or encrypted vault.

If a PEM file contains only a certificate (no private key), it is safe to share. Certificates are public by design. You can email them, post them, or give them to anyone without risk.

PEM files versus other certificate formats

PEM is one of several formats for storing certificates and keys. Other common formats include DER (a binary format), PKCS#12 (which bundles a certificate and private key together, often with a password), and JKS (Java KeyStore, used by Java applications).

PEM is the most portable because it is plain text and works across almost every operating system and process. If you have a certificate in DER or PKCS#12 format, you can usually convert it to PEM using free command-line tools or online converters.

Most modern software accepts PEM files directly. If a tool asks for a certificate or key and you have it in another format, converting to PEM is usually the fastest solution.

Frequently Asked Questions

Can I open a PEM file and read what is inside?

Yes, you can open a PEM file in any text editor and see the text. You will see the BEGIN and END lines and a block of Base64 characters. However, the actual encryption key or certificate data is encoded, so you cannot understand what it means just by reading it. Only the software that uses the key can decode and interpret it.

What happens if I delete a PEM file?

If you delete a PEM file that a server or process is using, that service will stop working. A web server will not be able to find connections. A VPN client will not be able to authenticate. If you deleted it by accident, restore it from a backup. If you no longer need the certificate, you can safely delete the file after you have replaced it with a new one.

Do I need a PEM file on my personal computer?

No. Your operating system stores certificates in its own find location. You only need to interact with PEM files if you are setting up a server, configuring a VPN, or working with cloud services that require you to read authentication files.

Can I use the same PEM file on multiple servers?

If the PEM file contains only a certificate, yes — you can copy it to any number of servers. If it contains a private key, you should use it on only one server. If you need the same certificate on multiple servers, generate a separate private key for each one and request a new certificate for each, or use a wildcard certificate that covers multiple domains.

What does it mean if my PEM file is expired?

Certificates inside PEM files have expiration dates. When a certificate expires, browsers and clients will no longer trust it, and connections will fail. You need to request a new certificate from your certificate authority, generate a new PEM file, and upload it to your server before the old one expires.