GlossaryPrivacy & SecurityIntermediate

SSL/TLS

SSL/TLS is the encryption protocol that secures data in transit on the web — the 'S' in HTTPS — protecting it from eavesdropping and tampering.

Last updated May 28, 2026

Definition

TLS (Transport Layer Security), the successor to the older SSL, is the cryptographic protocol that encrypts data as it travels between a client and a server. It is what puts the 'S' (and the padlock) in HTTPS, ensuring traffic cannot be read or modified in transit.

TLS and proxies

When you use an HTTP proxy with HTTPS, the proxy opens an encrypted tunnel (via the CONNECT method) that it cannot read. Some corporate setups perform TLS interception, decrypting and re-encrypting traffic to inspect it — which requires installing a trusted certificate.

Examples

1

The padlock icon and https:// shown when TLS secures a site

2

A proxy using CONNECT to tunnel an encrypted HTTPS session

Common Use Cases

Encrypting web traffic end to end
Authenticating server identity via certificates
Securing API and proxy connections

Frequently Asked Questions

TLS is the modern, more secure successor to SSL. The term 'SSL' is still used colloquially, but today's connections actually use TLS.
Not normally — it tunnels the encrypted connection. It can only read it if TLS interception is configured and you trust its certificate.

Keep Learning

All terms

DNS (Domain Name System)

DNS is the internet's phonebook — it translates human-readable domain names like example.com into the numeric IP addresses computers use to connect.

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HTTP Proxy

An HTTP proxy is an intermediary server that forwards web (HTTP/HTTPS) requests on your behalf, able to read, cache and filter traffic at the application layer.

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VPN

A VPN (Virtual Private Network) encrypts all of your device's internet traffic and routes it through a remote server, hiding your IP and protecting data on untrusted networks.

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