# PEM to DER Converter: Certificate, Key or CSR to Binary

> Convert PEM certificates, private keys and CSRs to binary DER in your browser, one file per object, for Windows, Java, Android and embedded devices.

Source: https://ssl.sh/tools/ssl-converter/pem-to-der/
Last updated: 2026-11-10

Convert PEM text (BEGIN/END blocks) into binary DER files, one per certificate, key or CSR. Runs locally in your browser.

The PEM to DER converter turns PEM-encoded objects into binary DER. Paste one or more PEM blocks (or choose a `.pem` file) and press **Convert**; each certificate, key or CSR is offered as its own `.der` download. Nothing is uploaded.

## When you need DER

- Installing a CA certificate on Android or some Linux-based devices that only accept DER.
- Java `keytool -importcert` accepts both, but some older tools and appliances require DER.
- Embedding a certificate in firmware or an IoT SDK as a byte array.
- Windows "Certificate Export Wizard" style workflows that expect `.cer` binary files.

## Steps

1. Paste PEM text, for example a block starting with `-----BEGIN CERTIFICATE-----`.
2. Press **Convert**.
3. Download each DER file. Certificates are named after their Common Name.

## Equivalent OpenSSL commands

```bash
openssl x509 -in cert.pem -outform DER -out cert.der
openssl req -in request.csr -outform DER -out request.der
openssl pkey -in privkey.pem -outform DER -out privkey.der
```

## Tips

- To check the result, open the `.der` file in the [certificate decoder](https://ssl.sh/tools/certificate-decoder/); it reads DER directly.
- For a C array, `xxd -i cert.der` prints the bytes ready to paste into source code.


## FAQ

**Why do I get several files?**

DER has no way to store more than one object per file. Each PEM block (leaf, each intermediate, key) becomes its own DER file. Use PFX or P7B if you need one file for a whole chain.

**Should the file end in .der or .cer?**

Both are common for DER certificates. Windows associates .cer with its certificate viewer and opens both DER and PEM .cer files.

**Does an encrypted PEM key stay encrypted?**

Yes. An ENCRYPTED PRIVATE KEY block becomes an encrypted PKCS #8 DER file; the password is unchanged.