A TLS fingerprint is a signature derived from the Client Hello message during a TLS handshake. Fields such as cipher order, extensions, ALPN, and key share groups differ between Chrome, Firefox, Node.js, Python requests, and other HTTP stacks.
Common formats include JA3 (MD5 hash) and JA4 (newer, with truncated SHA256 segments), plus HTTP/2 Akamai fingerprints from captures on tls.peet.ws.
Learn more in What is TLS fingerprinting?, analyze captures with the TLS Capture Analyzer, or see Fingerprinting Resources.