Implementation:Microsoft Playwright Client Coverage

Knowledge Sources	Microsoft_Playwright
Domains	Browser Automation, Code Coverage
Last Updated	2026-02-12 00:00 GMT

Overview

Concrete tool for collecting JavaScript and CSS code coverage data from Chromium-based browsers provided by the Playwright library.

Description

The Coverage class implements the api.Coverage interface and wraps the page channel's coverage-related methods. It provides paired start/stop methods for both JavaScript and CSS coverage collection. startJSCoverage() and startCSSCoverage() accept options to configure coverage collection (such as resetting counters or reporting anonymous scripts). The corresponding stopJSCoverage() and stopCSSCoverage() methods return arrays of coverage entries containing URL, source text, and range information.

Usage

Use the Coverage class when you need to measure which JavaScript or CSS code was executed during page interactions. This is available only in Chromium-based browsers. Access it via page.coverage.

Code Reference

Source Location

• Repository: Microsoft_Playwright
• File: packages/playwright-core/src/client/coverage.ts

Signature

export class Coverage implements api.Coverage {
  private _channel: channels.PageChannel;

  constructor(channel: channels.PageChannel);

  async startJSCoverage(options?: channels.PageStartJSCoverageOptions): Promise<void>;
  async stopJSCoverage(): Promise<channels.PageStopJSCoverageResult['entries']>;
  async startCSSCoverage(options?: channels.PageStartCSSCoverageOptions): Promise<void>;
  async stopCSSCoverage(): Promise<channels.PageStopCSSCoverageResult['entries']>;
}

Import

import { Coverage } from 'playwright-core/src/client/coverage';

I/O Contract

Inputs

Name	Type	Required	Description
channel	channels.PageChannel	Yes	The page channel to send coverage commands through (constructor parameter)
options (startJSCoverage)	PageStartJSCoverageOptions	No	Options such as resetOnNavigation and reportAnonymousScripts
options (startCSSCoverage)	PageStartCSSCoverageOptions	No	Options such as resetOnNavigation

Outputs

Name	Type	Description
stopJSCoverage()	Promise<CoverageEntry[]>	Array of JS coverage entries with URL, source text, and function ranges
stopCSSCoverage()	Promise<CoverageEntry[]>	Array of CSS coverage entries with URL, source text, and ranges

Usage Examples

// Start JS coverage collection
await page.coverage.startJSCoverage();

// Navigate and interact with the page
await page.goto('https://example.com');
await page.click('button');

// Stop and retrieve coverage data
const jsCoverage = await page.coverage.stopJSCoverage();
for (const entry of jsCoverage) {
  console.log(`${entry.url}: ${entry.functions.length} functions`);
}

// CSS coverage
await page.coverage.startCSSCoverage();
await page.goto('https://example.com');
const cssCoverage = await page.coverage.stopCSSCoverage();

Related Pages

• Environment:Microsoft_Playwright_Node_Runtime_Environment