Inspect outbound Node.js traffic in the standard Chrome DevTools Network panel.

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Version 2 has two mutually exclusive backends:

• Native connects to Node's experimental Network Inspector without patching application network APIs.
• Legacy captures HTTP/HTTPS, Fetch, opted-in Undici, WebSocket frames, and SSE through a project-owned standard CDP target.

The runtime owns a target, not a Chrome process. Browser opening is explicit, ports default to OS assignment, and Legacy application transport uses isolated child-process IPC instead of the old 5270 WebSocket/lock-file design.

npm install --save-dev node-network-devtools

# Zero-code startup
npx nnd dev --open src/app.js

# Diagnose the actual runtime and adapter capabilities
npx nnd doctor --json

Library usage:

import { register } from 'node-network-devtools'

const registration = register({
  mode: 'auto',
  requiredCapabilities: ['responseBody'],
  inspector: { host: '127.0.0.1', port: 0 },
  devtools: { open: false }
})

const ready = await registration.ready
console.log(ready.mode, ready.target, ready.capabilities, ready.fallbackReason)

await registration.openDevtools()
await registration.dispose()

The handle remains callable for v1 compatibility: const unregister = register(); unregister().

Native values are probed from the running Node version and Inspector methods. Forced Native fails if requirements are missing; Auto returns a structured reason whenever it uses Legacy.

Native HTTP/2 is conservatively allowlisted only for Node 22.20+ releases in the 22.x line. A non-empty h2c lifecycle passed on Node 22.22.3, while consuming a non-empty response with setEncoding() crashes the upstream experimental Inspector on Node 24.16.0 and 26.8.1 with Missing dataLength. Other and future majors remain reported as unsupported until independently verified; Legacy does not capture HTTP/2.

Both backends support persistent Network sessions, external response bodies, HAR 1.2 export, traceparent correlation, and replay:

const registration = register({
  session: { directory: '.nnd/sessions/run-001', har: true }
})

await registration.ready
// run application traffic
await registration.dispose()

npx nnd replay --dry-run --json .nnd/sessions/run-001
npx nnd replay capture.har

Mock is intentionally Legacy-only. Auto selects Legacy when legacy.mock rules are configured; forced Native reports NND_NATIVE_MOCK_CONFLICT.

• npm package guide
• v1 to v2 migration
• v2 architecture and implementation evidence

The package requires Node.js >=18.18. Node 18 and 20 remain compatibility lanes for migrations despite being EOL; maintained Node releases are preferred. undici@^6 remains a peer dependency so opt-in Legacy interception can patch the application's package instance.