PEM to DER Converter

Convert certificates and keys from PEM format (Base64 text) to DER format (binary) for different applications and systems.

Overview

PEM to DER Converter strips the Base64 encoding and BEGIN/END headers from PEM-formatted X.509 certificates, private keys, public keys, and CSRs, producing the compact binary DER file that Java keystores, Windows certificate stores, and many mobile platforms require. The entire decoding and re-encoding step runs in your browser using JavaScript — no file is ever transmitted to a server, which matters when the input is a private key or a production TLS certificate. Paste the PEM text or drag in a .pem file and download the resulting .der, .cer, or .crt binary in seconds.

Common Use Cases

  • Java Keystore Import — Java's keytool and many JVM-based servers expect DER-encoded certificates; convert your PEM cert to .der before importing into a keystore.
  • Windows Certificate Store — Windows certificate management and IIS import workflows often require the binary .cer or .crt format rather than the text-based PEM file.
  • Mobile & Embedded Platforms — iOS, Android, and some embedded TLS stacks accept only DER binary certificates; this converter produces the correctly encoded file without any server-side tooling.
  • Private Key Format Migration — When moving private keys between systems that require binary DER encoding, convert RSA or EC PEM keys locally so the sensitive material is never uploaded.
  • Automated DevOps Pipelines — Developers validating certificate chains or preparing deployment artifacts can quickly check PEM-to-DER output in the browser before scripting the openssl equivalent.

How It Works
1

Input PEM Data

Paste your PEM-formatted certificate, key, or CSR with the BEGIN/END headers, or upload a .pem file.

2

Automatic Conversion

The tool decodes the Base64 content and converts it to binary DER format while preserving the cryptographic data.

3

Download DER File

Download the converted binary file with the appropriate extension (.der, .cer, .crt) for use in your target system.

Frequently Asked Questions

What's the difference between PEM and DER formats?
PEM is Base64-encoded text with BEGIN/END headers, human-readable and widely used. DER is binary format, more compact and preferred by some applications like Java keystores.

When should I use DER instead of PEM?
Use DER for Java applications, Windows certificate stores, some mobile platforms, and when you need the most compact binary representation of certificates.

Will conversion affect the certificate validity?
No, PEM to DER conversion only changes the encoding format. The cryptographic content, validity dates, and all certificate information remain identical.

Can I convert private keys as well?
Yes, the tool can convert PEM-formatted private keys, public keys, certificates, and CSRs to DER format while maintaining their cryptographic properties.

Is the conversion process secure?
Yes, all conversion happens locally in your browser. Your certificates and keys are never transmitted to external servers or stored anywhere.

Related Tools

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