Fluxzy

Fluxzy is a traffic-debugging proxy for developers and security engineers who need to inspect and alter HTTP traffic across desktop, mobile, and API clients. Its strongest fit is work that ordinary proxy setup cannot capture; the free edition, despite including all features, is restricted to personal use.

Overview

Fluxzy records, analyzes, and modifies HTTP/1.1, HTTP/2, and WebSocket traffic over plain or secure channels. Proxyless capture can collect HTTP and HTTPS traffic without proxy configuration, including from apps that ignore system proxy settings. That is a meaningful advantage when a client resists conventional interception. Android capture uses Fluxzy Connect through a local VPN, while iOS apps are routed to the proxy.

The tool works offline without an account or cloud sync, and Fluxzy states that it has no telemetry. Fluxzy.Core is open source under GPLv3, but the Desktop application is not, so Fluxzy is not an all-open-source desktop stack. Downloads have additional integrity signals: desktop checksums use SHA-256, CLI checksums use SHA-512, Windows binaries are Authenticode-signed, and macOS builds are signed and notarized.

Key features

Rules can edit request and response headers, inject authentication, simulate slow networks, forward requests, spoof DNS, change TLS fingerprints, and force HTTP versions. Breakpoints, traffic replay, response mocking, and proxy chaining extend the workflow beyond passive inspection, making Fluxzy useful for reproducing failures and checking how clients respond to controlled changes.

For API work, Fluxzy decodes gRPC and Protobuf traffic either without a schema or with real field names from .proto files. It can also inspect OpenAI, Anthropic, and Google Gemini requests and responses, including streaming responses and tool calls. That breadth is useful for teams debugging modern API clients, though the value depends on needing that protocol-level visibility.

Captures can be exported as HAR, Fiddler SAZ, PCAPNG for Wireshark, cURL commands, .http files, or native .fxzy files. This gives engineers options to move from inspection into other analysis and reproduction workflows. Official NuGet packages expose the Fluxzy engine to .NET Standard 2.1, .NET 6, and .NET 8 applications.

Pricing

Community is unusually broad in feature access, but its personal-use-only terms and identifying header rule it out for work. Pro is the straightforward paid option for an individual developer. Enterprise has a three-seat minimum, so it is less suitable for a small team that needs only one or two licenses. Both paid plans are perpetual one-time purchases, not recurring subscriptions. There is no free trial; Fluxzy offers a full refund if contacted within 14 days of purchase.

Platforms

Fluxzy supports Android, iOS, Linux, macOS, Windows, API workflows, and self-hosted use. Mobile capture is not identical across platforms: Android uses a local VPN through Fluxzy Connect, while iOS apps are routed to the proxy.

Who it's for

Fluxzy suits developers and security engineers who need to inspect difficult-to-capture app traffic, manipulate requests and responses, or debug gRPC and LLM API exchanges. Its export formats and .NET packages also help teams that need to carry captures into other tools or embed the engine in .NET applications. It is a weaker fit for professional users unwilling to pay, or for those requiring an open-source desktop application.

Pros and cons

• Pros: Proxyless capture handles applications that ignore system proxy settings, reducing setup friction for otherwise elusive traffic.
• Pros: gRPC/Protobuf decoding, LLM API inspection, traffic replay, and response mocking support investigation as well as reproduction.
• Pros: Multiple export formats and .NET engine packages make captures useful beyond the desktop application.
• Pros: Offline operation, no account requirement, and stated absence of telemetry suit workflows where cloud sync is unwelcome.
• Cons: The free edition is personal-use only and adds an x-fluxzy-community header, so business users must buy a license.
• Cons: Fluxzy Desktop is proprietary even though Fluxzy.Core is GPLv3, which limits the appeal for users seeking a fully open-source desktop tool.
• Cons: Enterprise starts at three seats, which can be excessive for smaller teams needing multi-user licensing.

Alternatives

Browse Web Debugging Proxies for more options. HTTP Toolkit is a freemium alternative with Android, iOS, Linux, macOS, web, and Windows support; its free Hobbyist plan includes basic interception and inspection, manual breakpoints, and built-in HTTP client tools. Reqable has a free Community plan limited to one device, 100MB of storage, and three rules in each of its rewrite, script, breakpoint, gateway, and mirror categories, so it may suit a tightly capped workflow; its Premium plan is $49.90 a year.

mitmproxy is a free, open-source interactive HTTPS proxy for readers who prioritize an open-source option. NetworkSpy has a free plan with limited LLM token-stream analysis, breakpoints, resource mapping, custom viewer building, and scripting. Mediator is a free, Apache-2.0-licensed cross-platform GUI gRPC debugging proxy, a focused alternative for gRPC work. Whistle is another free option. HTTPeep offers a Professional plan for $59, paid once as a single purchase with no subscription. Moni Proxy is a freemium option for macOS, Windows, iOS, Android, and Linux.

Verdict

Choose Fluxzy if you need deep traffic inspection and modification, especially proxyless capture, gRPC decoding, or visibility into streaming LLM API calls. Look elsewhere if work use must be free or the desktop application must be open source.