JA4 / JA3 TLS fingerprint decoder
Decode a JA4 TLS client fingerprint or a JA3 fingerprint into its fields, compute the hashed JA4 from raw values, or compute a JA3 MD5. It auto-detects which you paste. All in your browser.
Security & WAFComputed in your browser. Nothing is uploaded.
How a JA4 is built
A JA4 has three parts joined by underscores: JA4_a is human-readable (transport, TLS version, SNI, cipher count, extension count, ALPN); JA4_b is a truncated SHA-256 of the sorted cipher list; JA4_c is a truncated SHA-256 of the sorted extensions plus the signature algorithms. GREASE values are ignored throughout.
API endpointGEThttps://ronutz.com/api/v1/ja4-fingerprint-decoderDocumented, not served. Opens the specification.