@playwright-labs/network-core

Network condition emulation for Chromium over CDP — presets (GPRS → WiFi, offline), a validated condition factory, and a NetworkAPI handle with async-dispose cleanup.

Installation

pnpm add -D @playwright-labs/network-core

Quick start

import { test } from '@playwright/test';
import { NetworkAPI, createNetworkCondition, kbps } from '@playwright-labs/network-core';

test('page under slow 3G', async ({ page, context }) => {
  const session = await context.newCDPSession(page);
  await using network = new NetworkAPI(session);

  await network.start('Regular3G');          // preset by name
  await page.goto('/dashboard');
  // ...assertions under throttling...

  // scope exit (async dispose) restores normal networking
});

Presets

GPRS, Regular2G, Good2G, Regular3G, Good3G, Regular4G, DSL, WiFi, Offline, NoThrottling — exported as NETWORK_PRESETS, names typed as NetworkPreset.

| Preset | Download | Upload | Latency | |---|---|---|---| | GPRS | 50 Kbps | 20 Kbps | 500 ms | | Regular2G | 250 Kbps | 50 Kbps | 300 ms | | Good2G | 450 Kbps | 150 Kbps | 150 ms | | Regular3G | 750 Kbps | 250 Kbps | 100 ms | | Good3G | 1.5 Mbps | 750 Kbps | 40 ms | | Regular4G | 4 Mbps | 3 Mbps | 20 ms | | DSL | 2 Mbps | 1 Mbps | 5 ms | | WiFi | 30 Mbps | 15 Mbps | 2 ms |

Custom conditions

import { createNetworkCondition, kbps, mbps } from '@playwright-labs/network-core';

const flaky = createNetworkCondition({
  latency: 800,
  downloadThroughput: kbps(256),
  uploadThroughput: kbps(64),
});
await network.start(flaky);

• omitted fields mean "no restriction" (-1 throughput, 0 latency, online)
• validation: latency >= 0, throughput >= 0 or -1 (disable), finite numbers only — invalid input throws TypeError before any CDP call
• results are frozen

NetworkAPI

| Member | Behaviour | |---|---| | start(preset \| condition) | applies and returns the resolved frozen NetworkCondition; enables the CDP Network domain on first call | | stop() | restores normal networking; idempotent | | condition | currently applied condition or null | | started | boolean | | await using / Symbol.asyncDispose | stop() on scope exit |

Limitations

• Chromium only — CDP sessions are not available for Firefox/WebKit
• throttling applies per CDP session (page), not per context

License

MIT