Modify HTTP Headers in Web Automation Using Requestly

In this guide, we’ll walk through how to integrate Requestly into any browser-based automation framework (Selenium, Playwright, Puppeteer, etc.) to programmatically modify request and response headers.

Steps to Use Requestly for Header Modification in Automation

Install Chrome for Testing

Download Chrome for Testing, the automation-friendly version of Chrome.

Why Chrome for Testing?

Starting with Chrome 137, official Chrome builds no longer support the --load-extension flag due to security concerns. There commit →

To load extensions in automation tools (Selenium, Playwright, Puppeteer, etc.), you must use Chrome for Testing or Chromium.

Regular Chrome will block extension loading via automation. Use Chrome for Testing to avoid breakages and ensure compatibility.

Install the Automation Tool of Your Choice

npm install selenium-webdriver

Download the Requestly CRX Extension

Download the CRX file of the Requestly Extension.

Configure the Browser with the Extension

Use your automation tool’s configuration options to:

Set the path to Chrome for Testing binary
Add the Requestly CRX extension

For Javascript ( Node.js )

const { Builder } = require("selenium-webdriver");
const chrome = require("selenium-webdriver/chrome");
const path = require("path");

const options = new chrome.Options();
options.setChromeBinaryPath("/Path/to/chrome-for-testing"); 
options.addExtensions(path.resolve(__dirname, "requestly.crx"));  

const driver = await new Builder()
  .forBrowser("chrome")
  .setChromeOptions(options)
  .build();
// Now use driver.get() to navigate as needed...

For Python

from selenium import webdriver
from selenium.webdriver.chrome.options import Options

chrome_options = Options()
chrome_options.binary_location = "/Path/to/chrome-for-testing"
chrome_options.add_extension("/path/to/requestly.crx")

driver = webdriver.Chrome(options=chrome_options)
# driver.get(...) to open pages

For Java

ChromeOptions options = new ChromeOptions();
options.setBinary("/Path/to/chrome-for-testing");
options.addExtensions(new File("/path/to/requestly.crx"));
WebDriver driver = new ChromeDriver(options);
// driver.get(...) to open pages

Perform Header Modifications Using Automation URLs

Once the browser is launched with Requestly, hit the following URLs to programmatically apply rules:

Add Request Header

https://app.requestly.io/automation/add-request-header?<headerName>=<headerValue>

To add multiple headers, simply append them using the & symbol like this:
?header1=value1&header2=value2&header3=value3

Add Response Header

https://app.requestly.io/automation/add-response-header?<headerName>=<headerValue>

Remove Request Headers

https://app.requestly.io/automation/remove-request-header?<headerName>

To remove multiple headers, simply append them using the & symbol like this:
?header1&header2&header3

Remove Response Headers

https://app.requestly.io/automation/remove-response-header?<headerName>

Test on a Live Site

To verify if the headers are successfully modified, open https://testheaders.com in the automated browser and inspect the headers shown.

You may need to trigger a button click to reveal headers on some pages.

Complete Working Example in Selenium ( Javascript )

Here’s a working example using Selenium, but this logic can be adapted easily to Playwright, Puppeteer, or others.

const { Builder, By, until } = require("selenium-webdriver");
const chrome = require("selenium-webdriver/chrome");
const path = require("path");

(async () => {
  const options = new chrome.Options();

  options.setChromeBinaryPath("/Path/to/chrome-for-testing");
  options.addExtensions(path.resolve(__dirname, "requestly.crx"));

  const driver = await new Builder()
    .forBrowser("chrome")
    .setChromeOptions(options)
    .build();

  try {
    await driver.get("https://app.requestly.io/automation/add-request-header?x-testing=selenium");

    await driver.wait(
      until.elementTextContains(
        driver.findElement(By.tagName("body")),
        "Success"
      ),
      1000
    );

    await driver.get("https://testheaders.com");

    await driver.findElement(By.css("button")).click();

    await driver.wait(
      until.elementTextContains(
        driver.findElement(By.tagName("body")),
        "x-testing"
      ),
      5000
    );

    console.log("Header added and verified!");

  } catch (err) {
    console.error("Error during automation:", err);
  } finally {
    await driver.quit();
  }
})();