Best Way to Intercept XHR Requests on a Page with Puppeteer and Return Mock Responses

Best Way to Intercept XHR Requests on a Page with Puppeteer and Return Mock Responses

21 May 2024 Stephan Petzl Leave a comment Tech-Help

Intercepting XHR requests and returning mock responses can be crucial for backendless testing of web applications. This guide will walk you through the process using Puppeteer, a Node library that provides a high-level API to control headless Chrome or Chromium over the DevTools Protocol.

Step-by-Step Guide to Intercept and Mock XHR Requests

The key to intercepting XHR requests in Puppeteer is the request.respond() method. Below is a practical example:

Setup Request Interception

First, enable request interception on the page:

await page.setRequestInterception(true);


Intercept and Mock Responses

Next, use the page.on('request') event to intercept requests and provide mock responses:

page.on('request', request => {
    if (request.url() === '') {
            content: 'application/json',
            headers: {"Access-Control-Allow-Origin": "*"},
            body: JSON.stringify({ key: 'mocked response' })
    } else {



  • Enable request interception with page.setRequestInterception(true).
  • Intercept each request using page.on('request').
  • Match the request URL to your target endpoint.
  • If matched, respond with mock data using request.respond().
  • Allow other requests to continue with request.continue().

Important Considerations

  • Ensure CORS headers are set correctly, or access to the mock data will be denied.
  • Mock data should be structured as expected by the application.

Advanced Library Options

For more advanced scenarios, you may consider using libraries such as puppeteer-request-intercepter or Mockiavelli. These libraries provide additional capabilities and integrations with testing frameworks.

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