Transport Layer Security (TLS) is the standard cryptographic protocol that encrypts and authenticates internet communications across HTTPS, WebSockets, and APIs.
Transport Layer Security (TLS) is the foundational cryptographic protocol designed by the IETF to provide end-to-end data privacy, integrity, and endpoint authentication across computer networks. Operating directly above the TCP transport layer, TLS powers modern HTTPS, secure WebSockets (wss://), secure email protocols (STARTTLS, SMTPS, IMAPS), and API communications.
TLS is the modern, secure successor to the deprecated Secure Sockets Layer (SSL) protocol (SSL 1.0, 2.0, and 3.0 are now mathematically broken and prohibited).
Audit live domain TLS protocol versions, cipher suites, and certificate chains using our SSL/TLS Certificate Decoder or test secure WebSocket endpoints in real time with our WebSocket Tester.
| Specification | Technical Details |
|---|---|
| Current Standard | IETF RFC 8446 (TLS 1.3, August 2018) |
| Legacy Supported Version | IETF RFC 5246 (TLS 1.2, August 2008) |
| Deprecated / Insecure | SSL 2.0 (RFC 6176), SSL 3.0 (RFC 7568), TLS 1.0/1.1 (RFC 8996) |
| Default TCP Port | Port 443 (HTTPS), Port 853 (DNS over TLS), Port 8883 (MQTT TLS) |
| Key Exchange Mechanisms | Ephemeral Diffie-Hellman (ECDHE / DHE) providing Forward Secrecy |
| Symmetric Cipher Suites | AES-128-GCM, AES-256-GCM, ChaCha20-Poly1305 (AEAD only in TLS 1.3) |
TLS 1.3 represents the most comprehensive redesign in the protocol's history, focusing on speed and uncompromising security:
TLS 1.2 Handshake (2 Round-Trips / 2-RTT)
Client Server
│ ─── ClientHello ─────────────────► │
│ ◄── ServerHello + Certificate ─── │
│ ◄── ServerKeyExchange + Done ──── │
│ ─── ClientKeyExchange ───────────► │
│ ─── [Finished] ──────────────────► │
│ ◄── [Finished] ────────────────── │
│ ◄═══ Encrypted Application Data ═► │
TLS 1.3 Handshake (1 Round-Trip / 1-RTT)
Client Server
│ ─── ClientHello + Key Share ─────► │
│ ◄── ServerHello + EncryptedCert ─ │
│ ◄── [Finished] ────────────────── │
│ ─── [Finished] ──────────────────► │
│ ◄═══ Encrypted Application Data ═► │
| Feature / Property | TLS 1.2 (RFC 5246) | TLS 1.3 (RFC 8446) |
|---|---|---|
| Handshake Latency | 2 Round Trips (2-RTT) | 1 Round Trip (1-RTT); optional 0-RTT resumption |
| Static RSA Key Exchange | Supported (Vulnerable to key compromise) | Completely Removed |
| Forward Secrecy (PFS) | Optional (depends on cipher suite) | Mandatory across all supported ciphers |
| Legacy Broken Ciphers | Supported RC4, DES, 3DES, CBC modes | Removed (Only authenticated AEAD ciphers) |
| Certificate Privacy | Server Certificate transmitted in plaintext | Server Certificate encrypted during handshake |
| Cipher Suite Count | 300+ complex combinations | 5 streamlined, standardized AEAD cipher suites |
In TLS 1.3, cipher suite negotiation is vastly simplified. Each suite specifies only the symmetric encryption algorithm and the hash function used for the pseudorandom function (PRF):
TLS_AES_128_GCM_SHA256 (Default high-performance standard)TLS_AES_256_GCM_SHA384 (High-security enterprise standard)TLS_CHACHA20_POLY1305_SHA256 (Optimized for mobile devices without hardware AES acceleration)TLS_AES_128_CCM_SHA256 (Designed for constrained IoT devices)TLS_AES_128_CCM_8_SHA256 (Constrained IoT devices with short MACs)h2 for HTTP/2, h3 for HTTP/3, or http/1.1) without extra round-trips.Under static RSA key exchange, if an adversary records encrypted network traffic today and obtains the server's private key years later, they can retroactively decrypt all recorded historical sessions. Ephemeral Diffie-Hellman (ECDHE) generates unique temporary keys per session, guaranteeing Forward Secrecy (PFS).
"SSL" (Secure Sockets Layer) was originally created by Netscape in the 1990s. When standardized by the IETF in 1999, it was renamed "TLS" (Transport Layer Security). Although many still casually say "SSL certificate", modern HTTPS runs exclusively on the TLS protocol.
All major web browsers (Chrome, Firefox, Safari, Edge) permanently disabled TLS 1.0 and 1.1 in 2020. Servers configured without TLS 1.2 or TLS 1.3 will encounter connection termination errors (ERR_SSL_VERSION_OR_CIPHER_MISMATCH).
Free, browser-based utilities to test, generate, and inspect Transport Layer Security (TLS) payloads directly.
Decode PEM & X.509 certificates offline or inspect live SSL/TLS certificate chains with expiration countdowns and health checks.
Connect to WebSocket endpoints (ws:// or wss://) in real time to inspect frames, measure latency, test heartbeats, and debug payloads.
Analyze HTTP response headers for security, caching, and compliance issues.
Build and test HTTP API requests with headers, body, auth, and response visualization.