What is the difference between .CER and .CRT files?

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Installing and managing an SSL certificate can be a daunting task if you are not familiar with the different file formats such as CER and CRT. These two extensions may have caught your attention and you may be wondering what they are, how they differ and most importantly, how to convert one to the other.

It's not as complicated as it sounds, and with a little guidance you'll have the hang of these concepts in no time. So, are you ready to learn what the difference is between .cer and .crt ?

Table of contents

What is a CER file?
What is a CRT file?
What is the difference between .CRT and .CER?
How to convert CRT to CER?
How to convert CER to CRT?
Reasons to convert one certificate to another
What is a CER file?
A CER file , which stands for Certificate File , is a digital certificate file format. Digital certificates are used in public-key cryptography to secure communications over networks such as the Internet. They are a key component of the SSL/TLS protocols , which ensure the privacy and integrity of data transmitted between a user's web browser and a website.

CER file extensions usually indicate that the mobile app development service file is in binary format. However, it can also be in base64 format. You will often see these extensions used interchangeably with CRT files, which leads to some confusion. Although CER and CRT files essentially serve the same purpose, they differ in the way they are encoded.

The CER file contains the public key, information about the key owner, and the digital signature of the certification authority (CA) that issued the certificate. The digital signature allows the recipient of the certificate to verify its authenticity and ensure that it has not been tampered with.




In practice, CER files are often used to distribute and install SSL certificates on various software applications and devices. For example, web servers use SSL/TLS certificates stored in CER files to establish secure connections with web browsers.

What is a CRT file?
A CRT file , also known as a certificate file , contains only the public key and other digital certificate data, but not the private key . The private key is stored securely and confidentially in a file with the .key extension on the server or device where the certificate is stored.

CRT files can be used in secure connections, allowing the recipient to verify the authenticity of the sender's identity, ensuring that the information sent remains intact. Web servers often use SSL/TLS certificates stored in CRT files to establish secure connections with web browsers.

What is the difference between .CRT and .CER?
Are .cer and .crt the same thing? Almost. The main difference between the CER and CRT file extensions is convention and naming. Technically, there is no difference in the content or format of the digital certificate files.

The use of one file extension is often a matter of preference or system-specific conventions. Some systems may default to one extension, while others may default to another.

Microsoft platforms widely use the CER security file, while many Unix-based systems prefer the CRT format for SSL certificates for web servers.

CER and CRT files can be either binary or base64-encoded ASCII . The file extension does not determine the encoding. Instead, it is the content that does. CER files are often base64-encoded binary files, while CRT files are usually base64-encoded ASCII files.