Definition
SSL (Secure Sockets Layer) and its modern successor TLS (Transport Layer Security) are cryptographic protocols that encrypt traffic between a browser and a website, verify the server's identity, and stop eavesdroppers or tamperers reading or altering data in transit. When a site runs HTTPS instead of HTTP, an SSL/TLS certificate is doing this work: a small file on the server holding a public key and a chain of trust back to a certificate authority. Modern deployments use TLS 1.2 or 1.3 (SSL itself was retired years ago) with ECDSA or RSA keys, and certificates typically renew every 90 days if issued free by Let's Encrypt, or up to a year for paid options. Almost every site on the web now uses HTTPS, since browsers flag HTTP pages as "Not Secure" and search engines rank HTTPS higher. Most reputable hosts include automatic SSL on every plan, so there is rarely a reason to pay extra or configure it manually.
How it works
An SSL/TLS certificate is a small file installed on the web server that contains the public key used to encrypt connections and a chain of trust that browsers can verify. Modern certificates use ECDSA or RSA encryption and are issued by certificate authorities (CAs) like Let's Encrypt, Sectigo or DigiCert.
Why it matters
Without HTTPS, browsers warn visitors away from the site and search engines downrank it. With HTTPS, traffic is encrypted, the site looks trustworthy, and modern features (HTTP/2, service workers, geolocation, payment APIs) actually work. There is no good reason to run a production site without SSL in 2026.