What is a JA4 fingerprint?

JA4 fingerprint decoder

What client made this TLS connection? JA4 fingerprints describe a client’s TLS hello in one short string.

InstantPlain English + technicalFree, no sign-upComing soon

Coming soon

This tool is on the way. It will decode a pasted JA4 or JA4S fingerprint into the TLS details it describes.

About the JA4 fingerprint decoder

Decode a JA4 or JA4S TLS fingerprint into the protocol, TLS version, ciphers, extensions and ALPN it describes.

Every result comes in two styles: plain English for everyone, and the exact technical detail for engineers, with the raw JSON one click away.

Questions

A short string that describes how a client starts an encrypted (TLS) connection. Security teams use it to spot bots and malware, which start connections differently from real browsers.