DER to PEM Converter
Convert DER certificates to PEM format.
- Enter a hostname to fetch a live certificate, or paste a certificate PEM.
- Click Check SANs.
- Review Common Name, SANs list, certificate type, and validity.
-----BEGIN CERTIFICATE-----\nMIIFazCCA1OgAwIBAgIR...\n-----END CERTIFICATE-----
What is DER to PEM Conversion?
DER to PEM conversion transforms binary-encoded certificates into human-readable text format. DER (Distinguished Encoding Rules) is a binary format commonly used in Windows environments, while PEM (Privacy Enhanced Mail) is a Base64-encoded text format preferred in Unix/Linux systems and web servers.
This conversion is essential for certificate compatibility across different systems, platforms, and applications. Many web servers, applications, and tools require PEM format, making this conversion a critical step in certificate deployment workflows.
Why Convert DER to PEM?
🔄 1. Cross-Platform Compatibility
Enable certificates to work across different operating systems:
- → Windows to Linux: Move certificates from Windows CA to Linux servers
- → Legacy Systems: Support older applications requiring PEM format
- → Cloud Migration: Deploy certificates to cloud platforms
- → Container Deployment: Use certificates in Docker/Kubernetes
🌐 2. Web Server Requirements
Most web servers require PEM format:
- Apache HTTP Server configuration
- Nginx SSL certificate installation
- HAProxy load balancer setup
- Cloudflare custom certificate upload
- AWS Certificate Manager import
🔍 3. Certificate Analysis
PEM format enables easier certificate inspection:
- Human-readable Base64 encoding
- Compatible with OpenSSL command-line tools
- Easy to copy/paste in configuration files
- Viewable in text editors
- Suitable for version control systems
🔧 4. Development and Testing
Facilitate development workflows:
- Test certificates in development environments
- Debug SSL/TLS connection issues
- Integrate with CI/CD pipelines
- Automate certificate deployment scripts
Understanding Certificate Formats
📁 DER Format (Input)
Binary certificate format characteristics:
- Binary encoded, not human-readable
- Smaller file size than PEM
- Common file extensions: .der, .cer, .crt
- Native format for Windows Certificate Store
- Used by Java applications and some CAs
📄 PEM Format (Output)
Text-based certificate format benefits:
- Base64 encoded text, human-readable
- Begins with -----BEGIN CERTIFICATE-----
- Ends with -----END CERTIFICATE-----
- Compatible with most web servers
- Easy to copy/paste and edit
Common Use Cases
🏢 Enterprise Migration
Converting certificates when migrating from Windows-based infrastructure to Linux servers, cloud platforms, or containerized environments.
⚙️ Web Server Configuration
Preparing certificates for Apache, Nginx, or other web servers that require PEM format for SSL/TLS configuration.
☁️ Cloud Deployment
Converting certificates for deployment to AWS, Azure, Google Cloud, or other cloud platforms that prefer PEM format.
🔧 Development Tools
Making certificates compatible with OpenSSL, curl, development frameworks, and testing tools that expect PEM format.
💡 Conversion Best Practices
- ✓ Verify certificate integrity after conversion
- ✓ Keep original DER files as backup
- ✓ Test converted certificates in target environment
- ✓ Ensure proper file permissions (600 for private keys)
- ✓ Validate certificate chain completeness
- ✓ Document conversion process for compliance
🔗 Related Tools
Complete your certificate format conversion workflow: