A fast and fully streamed MITM proxy to intercept, record, and modify HTTP/1, HTTP/2, WebSocket, and gRPC traffic, whether in plain or secured with TLS.

Fluxzy is a man-in-the-middle (MITM) proxy that acts as both client and server, enabling interception and modification of HTTP traffic. It supports configuration-driven setups through rule files, allowing easy reuse and switching of configurations between CLI, .NET applications, and the Fluxzy Desktop application.

Installation

npm install -g @fluxzy/cli

Or run directly without installing:

npx @fluxzy/cli start --llo

Supported Platforms

| OS | Architectures | |---|---| | Windows | x64, x86, arm64 | | macOS | x64, arm64 | | Linux | x64, arm64 |

The correct platform binary is automatically selected at install time.

Supported Proxy Protocols

| Protocol | Description | |----------|-------------| | HTTP CONNECT | Standard forward proxy tunneling for HTTPS traffic | | SOCKS5 | Full SOCKS5 support with no-auth and username/password authentication (RFC 1928) | | Reverse Proxy | Secure (TLS) and plain HTTP modes for backend service proxying | | System Proxy | Transparent system-wide interception via OS proxy settings |

Protocol detection is automatic: clients can connect using either HTTP CONNECT or SOCKS5 on the same listening port.

Key Features

• Intercepts HTTP/1.1, HTTP/2, WebSocket, and gRPC traffic
• Captures and exports deciphered raw packets in PCAP format
• Exports sessions as HTTP Archive (HAR) or Fluxzy Archive
• Manages custom certificates
• Impersonates JA4 fingerprints and custom HTTP/2 settings
• Acts as a system-wide proxy

Traffic Modification

• Add, remove, or modify request and response headers
• Transform request and response bodies
• Mock or substitute request and response bodies
• Forward, redirect, spoof DNS, block connections
• Inject HTML snippets into request and response bodies
• Remove cache directives, add request and response cookies
• Serve static directory
• Provide a specific TLS certificate for a given host

Browse the directive search page to see all built-in actions available.

Quick Start

Start a basic proxy on localhost:

fluxzy start --llo

Test with curl:

curl -x 127.0.0.1:44344 https://www.fluxzy.io

Using Rule Files

Rules are defined in YAML. Create a rule.yaml file:

rules:
  - filter:
      typeKind: requestHeaderFilter
      headerName: authorization
      operation: regex
      pattern: "Bearer (?<BEARER_TOKEN>.*)"
    action:
      typeKind: FileAppendAction
      filename: token-file.txt
      text: "${authority.host} --> ${user.BEARER_TOKEN}\r\n"
      runScope: RequestHeaderReceivedFromClient
  - filter:
      typeKind: anyFilter
    action:
      typeKind: AddResponseHeaderAction
      headerName: fluxzy
      headerValue: Passed through fluxzy

Then start fluxzy with the rule file:

fluxzy start -r rule.yaml --install-cert -sp -o output.fxzy -c

| Option | Description | |--------|-------------| | -r | Load a rule file | | --install-cert | Install the default certificate (requires elevation) | | -sp | Register as system proxy | | -o | Save captured traffic to a fluxzy archive | | -c | Enable raw packet capture |

For more information about the rule syntax, visit the documentation.

Commands

Usage:
  fluxzy [command] [options]

Commands:
  start                                   Start a capturing session
  cert, certificate                       Manage root certificates
  pack <input-directory> <output-file>    Export to a specific archive format
  dis, dissect <input-file-or-directory>  Read a previously captured archive

Run fluxzy start --help for the full list of options.

Other Installation Methods

Fluxzy CLI is also available through other package managers:

Windows (winget):

winget install Fluxzy.Fluxzy

macOS (Homebrew):

brew tap haga-rak/fluxzy
brew install fluxzy

Docker:

docker run -it -p 44344:44344 fluxzy/fluxzy:latest start

Binaries are also available on the releases page.

Related

• Fluxzy Desktop - Cross-platform HTTP debugger GUI
• Fluxzy.Core - .NET library (NuGet)
• Documentation
• GitHub

License

GPL-3.0