Cloudflare uses JA3 and now JA4 TLS fingerprints, which are hashes of various TLS handshake parameters. https://github.com/FoxIO-LLC/ja4/blob/main/technical_de

Cloudflare uses JA3 and now JA4 TLS fingerprints, which are hashes of various TLS handshake parameters. https://github.com/FoxIO-LLC/ja4/blob/main/technical_details/JA4.md https://github.com/FoxIO-LLC/ja4/blob/main/technical_details... has more details on how that works, and they do offer an Nginx module: https://github.com/FoxIO-LLC/ja4-nginx-module https://github.com/FoxIO-LLC/ja4-nginx-module