TLS Handshake Visualizer

Watch HTTPS connections establish step by step

Version:

Speed:3×

💻Client
(Browser)

🖥️Server

TLS 1.2 vs TLS 1.3 Comparison

Feature	TLS 1.2	TLS 1.3
Round Trips	2-RTT	1-RTT
0-RTT Resumption	No	Yes (PSK)
Key Exchange	RSA, DHE, ECDHE	ECDHE only (forward secrecy mandatory)
Cipher Suites	~37 suites	5 suites (simplified)
Forward Secrecy	Optional	Mandatory
RSA Key Transport	Allowed	Removed
Server Hello Encrypted	No	After ServerHello
Certificate Encrypted	No (visible)	Yes (encrypted)
Downgrade Protection	Vulnerable	Built-in sentinel
Session Tickets	Optional extension	NewSessionTicket message
AEAD Ciphers	Optional	Required
Compression	Allowed (CRIME)	Removed
Renegotiation	Supported	Removed

TLS 1.3 Cipher Suites

Suite	Encryption	Hash
TLS_AES_128_GCM_SHA256	AES-128-GCM	SHA-256
TLS_AES_256_GCM_SHA384	AES-256-GCM	SHA-384
TLS_CHACHA20_POLY1305_SHA256	ChaCha20-Poly1305	SHA-256
TLS_AES_128_CCM_SHA256	AES-128-CCM	SHA-256
TLS_AES_128_CCM_8_SHA256	AES-128-CCM-8	SHA-256

What is TLS?

TLS (Transport Layer Security) is the protocol that secures HTTPS connections. It provides encryption, authentication, and integrity between a client and server.

TLS 1.3 Handshake Steps

ClientHello — Client sends supported cipher suites, key shares (ECDHE public keys), and SNI (server name)
ServerHello — Server selects cipher suite and key share. From here, traffic is encrypted
EncryptedExtensions — Server sends additional parameters (encrypted)
Certificate — Server sends its X.509 certificate chain (encrypted in TLS 1.3)
CertificateVerify — Server proves it owns the private key by signing the handshake transcript
Finished — Server sends MAC of entire handshake for integrity verification
Client Finished — Client verifies everything, sends its own Finished message

Key Exchange (ECDHE)

Both sides generate ephemeral key pairs on an elliptic curve (e.g., X25519). They exchange public keys and compute the same shared secret independently. This provides forward secrecy — even if the server's long-term private key is compromised later, past sessions remain safe.

Certificate Verification

Client checks certificate chain: server cert → intermediate CA → root CA
Root CA must be in the client's trust store
Client verifies cert hasn't expired and isn't revoked (OCSP/CRL)
Client checks SNI matches certificate's Subject Alternative Names (SAN)

0-RTT Resumption (TLS 1.3)

If client has a PSK (Pre-Shared Key) from a previous session, it can send application data in the very first message (0-RTT). Risk: 0-RTT data is replayable, so only safe for idempotent requests (GET).