Subtrace

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Introduction

Subtrace inspects HTTP requests in any server with a single command. You run your normal start command under subtrace run --, for example a FastAPI dev server or npm run dev, and it captures the requests and responses flowing through your backend without code changes.

That gives developers something like the browser’s network tab for server-side traffic, which is useful when debugging integration tests, third-party API calls and unexpected payloads. The README notes macOS support is in private beta with a waitlist; Linux works with the install script.

The source code is at subtrace/subtrace on GitHub under the BSD-3-Clause licence, with about 3,100 stars; the most recent commit was on 18 December 2025.

Launch and background: Y Combinator’s company directory lists Subtrace in its Winter 2025 batch, with the one-liner “Zero code network tracer”. Subtrace’s Product Hunt page lists it as launched in 2025.

Features

1. One-command capture: Wraps your existing start command.
2. No code changes: Inspect traffic transparently.
3. Request and response bodies: Full HTTP details.

Pros

1. Free to use: Open source under the BSD-3-Clause licence, so the core tool costs nothing to use.
2. Actively maintained: The repository had commits as recent as 18 December 2025.
3. Community: About 3,100 GitHub stars.

Cons

1. macOS in private beta: Linux is the primary platform.
2. Narrow scope: HTTP inspection rather than full observability.

Usage and Links (Example)

curl -fsSL https://subtrace.dev/install.sh | sh
subtrace run -- npm run dev
subtrace run -- fastapi dev main.py

Resources:

• Subtrace website
• GitHub repository

Pricing

Subtrace is free and open source under the BSD-3-Clause licence.

Recommended for?

1. Backend developers debugging HTTP traffic in tests and dev.

Conclusion

Subtrace is a handy, lightweight way to see what your server actually sends and receives.

Use it while writing integration tests.

On CheckOps, Subtrace is filed under the Integration testing, API & contract testing and Production monitoring & observability stages. Related tools listed here include mitmproxy, HTTP Toolkit, Sentry, OpenTelemetry, Jaeger and Honeycomb. A short trial on a real project, with your own code, data and pipeline, is usually the fastest way to choose between them, because fit matters more than feature lists. Facts here come from the official site, documentation and repository, checked on 11 November 2026.