.CRT File Extension
Security Certificate
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What is a CRT file?
A CRT file is an encoded digital certificate used by a secure website. It identifies the website and verifies its authenticity. CRT files may be saved in a variety of certificate formats, including the Distinguished Encoding Rules (.DER) and Privacy Enhanced Mail (.PEM) formats.
More Information
To host secure websites, web server administrators typically apply for digital certificates from third-party Certificate Authorities, such as GoDaddy, Verisign, or Thawte. These certificates are saved in various formats, including the CRT format.
After receiving a certificate, administrators must place it on their web server, within the website they want to secure. When a user accesses the site, the web server passes the certificate to the user's web browser, to verify the site's identity. (If a browser cannot verify a certificate, it may instead show a page that says "This website's certificate is expired.")
NOTE: To view the contents of a secure website's digital certificate, click the lock icon that appears in your website's address bar.
How to open a CRT file
You can use OpenSSL (multiplatform) to view the contents of a CRT file. For example, if your CRT file contains a certificate saved in the DER format, you can use the following command to view your file's contents:
openssl x509 -inform der -in YourFileName.crt -text -noout