An SSL certificate (also known as a TLS or SSL/TLS certificate) is a digital document that links a website's identification to a public-private cryptographic key pair. The certificate's public key lets web browsers start encrypted TLS and HTTPS sessions with web servers. The server secures the private key, which digitally signs web pages and other data (such as images and JavaScript files). An SSL certificate comprises a website's domain name and, optionally, its owner. Web browsers and operating systems will trust digitally signed material from a web server if its SSL certificate is certified by a reputable CA, like SSL.com. SSL certificates are X.509s.