What is a .pem file?
A .pem file is a X.509 CA certificate. Its registered MIME type is application/x-x509-ca-cert, which places it in the application or document family of formats.
CA stands for Certificate Authority.
Technically it is a specialised form of application/pkix-cert (the .cer format), so tools that understand that format can often read at least part of it.
PEM is a binary format: the contents are not readable text, so opening it in a text editor shows scrambled characters.
Files of this type usually begin with the bytes 2D 2D 2D 2D 2D 42 45 47 49 4E 20 43 41 20 43 45 52 54 49 46 49 43 41 54 45 2D 2D 2D 2D 2D. That signature is how programs recognise the format even when the extension is wrong or missing.
The same format is also saved with the extensions .cer, .cert, .crt, .der.
PEM file format details
| Extension | .pem |
|---|---|
| Format | X.509 CA certificate |
| MIME type | application/x-x509-ca-cert, application/pkcs7-mime, application/pkcs7-signature |
| Category | Application or document |
| Text or binary | Binary |
| Based on | application/pkix-cert |
| File signature | 2D 2D 2D 2D 2D 42 45 47 49 4E 20 43 41 20 43 45 52 54 49 46 49 43 41 54 45 2D 2D 2D 2D 2D |
| Registered with IANA | Yes |
| Other extensions | .cer, .cert, .crt, .der |
How to open PEM files
| Windows | PEM files (X.509 CA certificate) are made by specific software. The reliable way to open one is with the program that created it; a generic viewer will only show raw data. |
|---|---|
| Mac | The same applies on a Mac: look for a Mac version of the program that makes PEM files. |
| iPhone and iPad | Phones rarely open this type of file directly. The viewer above can show what is inside it without installing anything. |
| Android | The same applies on Android. The viewer above shows the first bytes of the file so you can confirm what it is. |
Can you convert a .pem file?
TapToConvert does not convert PEM files. The usual route is to open the file in the program that made it and use its Export or Save as option.
PEM file FAQ
What is a .pem file?
A .pem file is a X.509 CA certificate, with the MIME type application/x-x509-ca-cert.
How do I open a .pem file?
With the program that created it. The viewer on this page shows what is inside without installing anything.
Is a .pem file safe to open?
PEM files hold data rather than programs, but any file from an unknown source can be crafted to exploit the software that opens it. Keep that software up to date. The viewer on this page only reads the bytes and never runs anything.
What is the MIME type of .pem?
application/x-x509-ca-cert, and it is also seen as application/pkcs7-mime or application/pkcs7-signature. Web servers send this type so browsers know how to handle the file.
Is PEM a text or binary format?
Binary. Its contents are not readable as text.
File type facts come from the IANA media type registry, the mime-db project and the freedesktop.org shared MIME database.