CER, Internet Security Certificate (.cer)

The CER Website file format

CER files are security files provided and generated by an Certificate Authority. These files help a browser to verify if a website is secure and save to enter, verifying its authenticity. These CER security certificates are usually installed on a web server. If a user enters a URL to a website hosted on the same server, the browser checks the validity of the website by calling the certificate attached to it.

Technical details of CER files

The public certificate inside the CER file maps a public key with a certain identity using a digital signature, thus verifying a website. Different encoding algorithms like Base64 and DER can be used to encode the contents of the CER file. When browsing a validated site, the according CER file can be accessed by clicking on the lock icon on the browser window (usually located near the edge). This is available for websites with SSL encryption and can easily determined by the "https://" prefix of the URL. Double-clicking on said lock icon allows you to view the information contained in the CER file, at least in IE, Firefox and Safari.

More information about the CER file format

File extension .cer
File category Website
Associated programs Adobe Acrobat DC (Windows & Mac)
Adobe Reader (Windows, Mac & Linux)
Apple Keychain Access (Mac)
Apple Safari (Mac)
Microsoft Internet Explorer (Windows)
Mozilla Firefox (Windows)

Other Web Browsers
Useful links More About The Public Key Certificate And CER
Developer N/A
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