How To Convert Files from CRT to CER and CER to CRT
CER and CRT are two common file extensions used for digital certificates. CER files contain encoded certificates in a binary DER format while CRT files contain Base64 encoded certificates in a text format.
While CER and CRT files contain essentially the same certificate data, they use different encoding formats. This means they are not directly interchangeable. To convert a certificate between CER and CRT formats requires decoding and re-encoding the certificate data.
This article will explain the key differences between CER vs CRT files, why you may need to convert between formats, and provide simple step-by-step instructions for converting certificates on Windows and Linux systems.
Key Differences Between CER vs CRT Files
Here are the main differences between CER and CRT certificate files:
The core certificate data is identical. But the different encodings mean the actual file contents will differ. This is why the files are not interchangeable without conversion.
Why Convert Between CER and CRT?
There are a few common scenarios where you may need to convert a certificate file between CER and CRT format:
So, while conversion between CER and CRT is rarely essential, it can help make certificates more portable and usable across various systems and software.
Converting CRT to CER on Windows
Windows provides built-in tools to simply convert certificates from CRT to CER format:
certutil -encode input.crt output.cer
Using Windows Certificate Manager
The CRT has now been converted and exported as a CER file.
Converting CER to CRT on Windows
Windows also makes it easy to go the other direction – converting CER to CRT:
certutil -decode input.cer output.crt
Using Windows Certificate Manager
This exports and converts the certificate to CRT format.
Converting CER and CRT on Linux
The openssl command provides an easy way to convert certificates between CER and CRT on Linux and Unix systems:
openssl x509 -inform PEM -in input.crt -out output.cer
This decodes the CRT file and encodes to CER.
openssl x509 -inform DER -in input.cer -out output.crt
This decodes the CER file and encodes to CRT.
The openssl tool is included by default on most Linux distributions, providing a simple conversion solution.
Alternative Conversion Options
A few other options for CER/CRT conversion include:
However, the Windows and Linux command line methods outlined above provide the simplest and most accessible options for most users.
Troubleshooting CER/CRT Conversion Issues
Here are some troubleshooting tips for potential issues when converting certificates between CER and CRT formats:
If you still cannot convert between CER and CRT formats, it is worth double-checking the steps, encodings, and certificate validity to troubleshoot the issue.
Conclusion
Converting between the CER vs CRT files format is straightforward using the built-in tools on Windows and Linux. While the encoding differs, both CER and CRT contain the same core certificate data. Converting between the two allows using digital certificates across various software and systems that may only support one format. With the help of utilities like Certutil, Certificate Manager and OpenSSL, you can easily convert certificates from CER to CRT and vice versa. The ability to interconvert certificates helps make them more portable and usable across different environments. Whether you need CER or CRT format, you can encode your certificates into the required format using the simple command line tools outlined here.
Frequently Asked Questions
What is the difference between CER vs CRT files?
CER uses binary DER encoding while CRT uses Base64 text encoding, but both contain the same certificate data.
When would I need to convert a CER to CRT or vice versa?
When importing/exporting certificates to systems that require a specific format, or to view/edit certificates in text format.
Can I just change a .cer file extension to .crt?
No, the file contents are different and won’t be recognized properly without converting the encoding.
Is there an online tool for CER/CRT conversion?
Yes, various websites provide free online conversion tools to encode/decode between CER and CRT.
How do I convert CER/CRT on Mac or Linux?
OpenSSL provides command line utilities on Mac, Linux and UNIX for conversion between various certificate formats.
Do CER and CRT files contain private keys?
No, they only contain public certificate data, not the private key. To convert a PKCS#12 file containing a private key, use OpenSSL.
