Performance Benchmarking Using Playwright

When building modern web applications, performance is as crucial as functionality. Fast-loading pages, smooth user interactions, and optimized resource usage directly impact user experience and retention. To ensure this level of performance, developers and QA engineers often use performance benchmarking tools. One emerging tool that combines end-to-end testing capabilities with performance insights is Playwright.

In this blog, we’ll explore how to perform performance benchmarking using Playwright, understand the metrics you can capture, and how to use this data to make informed decisions.


What is Playwright?

Playwright is an open-source automation library developed by Microsoft that enables developers to script browser actions using JavaScript, TypeScript, Python, Java, or C#. It supports Chromium, Firefox, and WebKit, and is widely used for end-to-end testing.

But beyond testing functionality, Playwright also provides mechanisms to measure and monitor performance using browser context and DevTools Protocol, making it a lightweight yet powerful benchmarking tool.


Why Use Playwright for Performance Benchmarking?

While tools like Lighthouse or WebPageTest are designed for performance audits, Playwright offers unique benefits:

Automation + Performance: Combine functional tests with performance checks in one script.

Multi-Browser Support: Test performance across Chromium, Firefox, and WebKit.

Custom User Flows: Benchmark real user interactions instead of just initial page load.

DevTools Integration: Access detailed performance metrics using the Chrome DevTools Protocol.


Setting Up Playwright

Install Playwright via npm:


bash

npm install -D @playwright/test

npx playwright install

Then, create a basic test file (e.g., performance.spec.ts) and start writing scripts to measure performance.


Capturing Performance Metrics

To benchmark performance, you can use the page.metrics() method or capture tracing and HAR files.


Example: Using page.metrics()

javascript


const { test, expect } = require('@playwright/test');


test('Benchmark page load time', async ({ page }) => {

  const start = Date.now();

  await page.goto('https://example.com');

  const loadTime = Date.now() - start;

  console.log(`Page Load Time: ${loadTime} ms`);


  const metrics = await page.metrics();

  console.log(metrics);

});

This gives you page load time and browser-level metrics like JSHeapUsedSize, Nodes, Documents, and more.


Tracing and HAR Recording

Playwright also supports tracing to capture screenshots, snapshots, and performance details:


javascript


await page.context().tracing.start({ screenshots: true, snapshots: true });

await page.goto('https://example.com');

await page.context().tracing.stop({ path: 'trace.zip' });

You can view the trace.zip file using Playwright Trace Viewer to analyze execution steps and performance delays.


To record a HAR file (HTTP Archive), which is helpful for network analysis:


javascript


const context = await browser.newContext({ recordHar: { path: 'network.har' } });

const page = await context.newPage();

await page.goto('https://example.com');

await context.close();


Benchmarking Use Cases

  • Page Load Time: Measure time taken for full page load across different environments.
  • API Response Times: Track latency of backend services.
  • UI Interaction Speed: Measure the time taken for actions like button clicks or modal openings.
  • Resource Usage: Monitor memory usage, DOM node counts, and script evaluation time.


Best Practices

  • Run benchmarks in headless mode for consistency.
  • Repeat tests multiple times and average the results to reduce variance.
  • Use CI/CD pipelines to monitor performance regressions after each code change.
  • Compare performance across different browsers and screen resolutions.


Conclusion

Performance benchmarking is no longer just the responsibility of DevOps or performance engineers—developers and testers can now include it in their workflows using Playwright. With its ability to simulate real-world user flows and capture detailed metrics, Playwright empowers teams to build not only functional but also fast and efficient web applications. Start integrating performance tests today and deliver experiences your users will love.

Learn Playwright Testing Training
Read More: Advanced Selectors: nth, has, and filter in Playwright


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