Transparent Capture: Intercept Traffic With No Proxy Configuration

Capturing an application's HTTP traffic usually starts with pointing it at a proxy: enabling the system proxy, setting HTTP_PROXY, changing a browser setting, or wiring up an SDK. This works for applications that read those settings, but many do not. Some ignore the system proxy, some ship their own network stack, some hard-code their endpoints, and some expose no proxy setting at all. Each of these is a gap in what you can observe.

Transparent capture removes the proxy step. When it is enabled, Fluxzy records the traffic of every application on the machine, including browsers, command-line tools, desktop applications, and background services, without changing any proxy setting. Applications run unmodified and are captured as they are.

The difference between classic mode and transparent capture is where interception happens. A traditional proxy asks each application to send its traffic to a specific address. A transparent proxy works one layer lower, at the operating system's network routing, so applications do not need to know a proxy exists.

In practice this means:

• No system proxy to toggle, no environment variables to set, and no per-application configuration.
• Applications that ignore proxy settings or pin their own configuration are captured like any other. There is no proxyless blind spot to work around.
• Capture is global by default, and can then be narrowed to a specific process or set of hostnames.

Once traffic reaches Fluxzy, everything works as it does in classic proxy mode: live inspection, HTTPS decryption, search, filtering, request and response editing, replay, and export. Transparent capture also runs on Windows, Linux, and macOS, each using its own native networking facilities under the hood while the capture experience stays the same.

Transparent capture is selected when you start a capture.

Its behavior is configured in Global Settings, under the transparent proxy section.

Instead of asking each application to use a proxy, Fluxzy intercepts traffic at the operating system's network routing layer:

1. Fluxzy brings up a temporary virtual network adapter and asks the OS to route outbound traffic through it.
2. Captured packets are passed to the same Fluxzy engine used in classic proxy mode, which records, decrypts, inspects, alters, and replays them.
3. Responses travel back to the original application over the same path.

The application sees a normal network connection.

Rerouting a machine's network is a significant operation, and transparent capture is built to handle it carefully:

• The network changes apply only while a capture is running. Stopping the capture, or closing the application, restores networking automatically.
• The redirection is designed to recover connectivity on its own even if the application is force-closed, so it does not strand the connection.
• Setting up the virtual adapter requires elevated rights, so Fluxzy uses a small, dedicated privileged helper for that step while the main application keeps running unprivileged. A summary of the changes and a single authorization prompt are shown before anything is applied.

The interception engine, the part that records, decrypts, and replays traffic, is Fluxzy.Core, which is open source. It is the same engine used in classic proxy mode; transparent capture changes how traffic reaches the engine, not what happens once it arrives.

---

Transparent capture is currently in preview. Behavior and platform support continue to evolve, and feedback is welcome.