Stands for "Secure Socket Layer."

SSL is a technology for authenticating and encrypting data transfers over the Internet. It encrypts data transfers between a user's web browser and remote web servers, protecting user data like login credentials and credit card numbers. SSL was first released to the public in 1995 and was replaced in 1999 by a successor technology called TLS — although the successor is often also referred to as SSL.

SSL encrypts data traveling over the Internet to protect it from eavesdropping by other devices along the route. The HTTPS protocol uses SSL and TLS to secure regular web traffic, and other protocols for email (SMTP and IMAP), VPN connections, and file transfers (FTPS) also use it to encrypt and protect data. SSL uses authentication certificates (called SSL certificates) to authenticate the identities of the web server and its owner and administrator.

When first introduced, SSL was primarily used by e-commerce websites to protect a customer's credit card number, address, and other personal information during transactions. It was also used to obscure the username and password used during the login process for any site that allowed users to create accounts. Eventually, many websites started using SSL encryption for all data transfers between a client and server to keep browsing activity private thanks to incentives by search engines (who would reward secure sites by placing them higher in search results) and web browsers (which began labeling sites not using SSL as "not secure").


SSL technology was replaced in 1999 by the release of TLS 1.0. TLS addressed several shortcomings and vulnerabilities present in SSL. The first few releases of TLS were backward compatible with SSL, allowing older web browsers and website hosts to continue operating using a lower level of security. TLS 1.2, released in 2008, finally removed backward compatibility after nearly a decade of support.

TLS improves on the earlier SSL technology in several ways. It streamlined the handshake process to require fewer steps and speed up connections. It also uses more modern encryption algorithms like AES and ChaCha20-Poly1305 instead of the older DES and RC4 algorithms used by SSL.

Updated December 14, 2023 by Brian P.

quizTest Your Knowledge

What was DNSSEC created?

To simplify DNS management
To make DNS lookups faster
To improve DNS security
To make DNS compatible with IP6
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