JA3 fingerprints turn the TLS handshake into a passive identifier of the client stack. With setJa3FingerPrintAction you decide which signature Fluxzy presents to the upstream, which is essential when an API filters by fingerprint or when you need to reproduce a captured session with byte for byte fidelity.
setJa3FingerPrintAction controls the JA3 fingerprint that Fluxzy advertises to the upstream during the TLS handshake. JA3 is a hash of selected TLS ClientHello fields, and many providers use it to identify the client behind the request.
Common reasons to set it:
Combine with impersonateAction when you need both a JA3 fingerprint and a matching set of HTTP headers and ALPN behaviour.
Useful when an upstream blocks requests that do not look like a real browser. The fingerprint string is the JA3 hash that matches the target browser version.
rules:
- filter:
typeKind: HostFilter
pattern: api.partner.example.com
actions:
- typeKind: SetJa3FingerPrintAction
value: 771,4865-4866-4867-49195-49199-49196-49200-52393-52392-49171-49172-156-157-47-53,0-23-65281-10-11-35-16-5-13-18-51-45-43-27-17513,29-23-24,0
Replay traffic against an upstream by feeding back the exact JA3 fingerprint observed during the original capture session.
rules:
- filter:
typeKind: HostFilter
pattern: legacy.example.com
actions:
- typeKind: SetJa3FingerPrintAction
value: 771,4865-4867-4866-49195-49199,0-23-65281-10-11-35,29-23-24,0
Set a JA3 fingerprint of ongoing connection.
Evaluation scope defines the timing where this filter will be applied.
requestHeaderReceivedFromClient This scope occurs the moment fluxzy parsed the request header receiveid from client
setJa3FingerPrintAction
The following table describes the customizable properties available for this action:
| Property | Type | Description | DefaultValue |
|---|---|---|---|
| value | string |
This filter has no specific usage example
View definition of SetJa3FingerPrintAction for .NET integration.
This action has no related action
It is a hash computed over a specific list of TLS ClientHello fields: version, cipher suites, extensions, elliptic curves, and elliptic curve point formats. The exact format is documented by the JA3 project on GitHub.
impersonateAction applies a full client profile, including HTTP headers and ALPN values, that matches a known browser. setJa3FingerPrintAction is lower level and only controls the JA3 portion of the TLS handshake.
Capture it from the client you want to mimic, or pick a published value from the JA3 fingerprints database. Make sure the value matches the TLS stack you want Fluxzy to advertise.
No. Fingerprinting is one of many signals. JA3 alone does not bypass detection systems that also inspect headers, timing, or behavioural patterns.