.pfx

What is a .pfx file?

PFX is Microsoft's name for the PKCS#12 format — a password-protected bundle of certificate and private key.

Use caution
Type Security
By Microsoft / RSA Laboratories
MIME application/x-pkcs12

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What is it

PFX and P12 are the same format with different names. Microsoft calls it PFX (Personal Information Exchange). The rest of the world calls it PKCS#12 or P12. The file contains a certificate, its private key, and optionally the certificate chain, all protected by a password.

Windows uses .pfx as the default extension when exporting certificates with private keys from the Certificate Manager, IIS, or Active Directory Certificate Services. Azure, IIS, and other Microsoft services expect .pfx when you upload SSL certificates.

Renaming .pfx to .p12 (or vice versa) works perfectly — the file format is identical. OpenSSL, Keychain Access, and every certificate tool that handles P12 handles PFX, and vice versa. The dual-naming causes endless confusion, but once you know they're the same thing, the confusion disappears.

Technical details
Full Name
Personal Information Exchange
MIME Type
application/x-pkcs12
Developer
Microsoft / RSA Laboratories
Magic Bytes
30 82
Safety
.pfx requires caution. Contains private keys. Password-protected but handle with extreme care.
What opens it
Windows Certificate Manager
FREE Windows
Keychain Access
FREE Mac
KeyStore Explorer
FREE Windows / Mac / Linux
FAQ
Is PFX the same as P12?
Yes. Identical format, different extension. .pfx is Microsoft's convention; .p12 is the PKCS#12 standard. Renaming between them works perfectly.
How do I create a PFX from separate cert and key files?
`openssl pkcs12 -export -out bundle.pfx -inkey key.pem -in cert.pem -certfile chain.pem`. You'll be prompted to set a password for the PFX file.
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