Developer / Certificates

PEM and DER Converter

Convert certificate, key and CSR data between PEM and binary DER, base64 or hexadecimal, with type detection and RSA PKCS#1/PKCS#8 conversion.

PEM and DER Converter: Checks the encoding, identifies supported certificate, request and key structures, and writes PEM or DER downloads. Keeping the structure preserves the exact DER bytes. RSA private keys can also be wrapped as PKCS#8 or unwrapped as PKCS#1. Runs 100% locally in your browser with zero server file uploads.

Category
Developer tools
Runs
In your browser
Cost
Free · no sign-up
Availability
Ready to use
PEM and DER converterLocal processing

Runs entirely in your browser

PEM labels and encodings

RFC 7468 (https://www.rfc-editor.org/rfc/rfc7468) defines PEM textual encodings for certificates, requests and keys. The detected structure must agree with the label.

RSA key containers

RFC 8017 (https://www.rfc-editor.org/rfc/rfc8017) defines RSA key structures, and RFC 5208 (https://www.rfc-editor.org/rfc/rfc5208) describes PKCS#8 private key containers. Conversion does not verify signatures or decrypt keys.

How to use it

  1. Paste PEM, base64 or hexadecimal, or choose a binary DER file.
  2. Keep the structure or choose an RSA private key conversion.
  3. Convert, review the detected type and download PEM or DER.

Privacy & limitations

Everything runs in your browser. Your images, keys and pasted data are not uploaded or saved by this tool.

Related tools

Certificate decoderCSR DecoderKey Pair Generator

Frequently asked questions

Does PEM to DER change the key?

Keeping the structure changes only the text or binary representation. RSA private key conversion changes the container while retaining the same key material.

Can this decrypt an encrypted key?

No. Encrypted PKCS#8 containers can be re-encoded, but this tool does not decrypt them or validate their contents.

What inputs are supported?

One certificate, CSR, public key or private key at a time. PKCS#8, RSA PKCS#1 and EC SEC1 key structures are recognised. Binary files must be DER, not text files containing PEM.

Free tool · runs in your browser · no account required