Puppeteer for Localization Testing: Tips and Tricks

Localization testing isn’t just about getting the language right—it’s about delivering the right experience for every user, wherever they are. This includes pricing, layout behavior, and local content that adapts to the user's geography.

Puppeteer helps by automating real browser behavior, and WonderProxy takes it a step further by letting you run those tests from cities around the world. Together, they give you the visibility you need to test with real-world context.

Just keep in mind: WonderProxy can only access publicly available environments. To test staging or development, you’ll need to allow traffic from WonderProxy’s IPs through your firewall.

Why Puppeteer and localization go hand in hand

Once you’ve nailed down your localized content, the next challenge is to make sure it displays correctly for users in different regions. That’s where Puppeteer comes in.

Unlike API-level testing tools that only confirm backend responses, Puppeteer controls a full browser session. It renders the entire page, loads external scripts, applies CSS, and interacts with the DOM, just like a real user would.

That level of control is especially helpful for localization. You can automate visits from different locations, interact with elements on the page, and take screenshots or run assertions to confirm localized components are behaving as expected. It’s also ideal for identifying visual and behavioral issues that may not be apparent in static testing.

With Puppeteer, you’re equipped to test not just the presence of translated content but how it behaves once it’s rendered. It allows you to determine how your site performs across various regions, screen sizes, and connection speeds.

Setting up Puppeteer for proxy-based testing

Getting Puppeteer up and running is pretty straightforward. You install it with npm, launch a browser instance, open a new page, and start scripting interactions, including clicks, navigation, screenshots, and more. But if you’re testing localization, you’ll want to take things a step further and route that browser traffic through a proxy.

Your browser’s IP determines the content it sees. Without a location-specific IP, you might think you're testing from Tokyo, but you're still getting the U.S. version. That’s where proxy configuration comes in.

Puppeteer lets you pass proxy settings when launching the browser using the --proxy-server flag. This is where WonderProxy becomes essential. With its global network of city-level proxies, you can test how your site behaves in Berlin, São Paulo, or Singapore without leaving your desk. If localization is the goal, location-aware proxying is what makes the whole thing real.

Using WonderProxy to reflect real-world locations

WonderProxy makes it easy to simulate real-world user locations by routing traffic through proxy servers worldwide. Instead of guessing how your site behaves in Madrid or Seoul, you can load it from those locations and see exactly what local users would experience. It's a reliable way to test regional content, language settings, and localized pricing.

By default, tests will run against your production environment since WonderProxy can only reach publicly accessible resources. To test staging or development environments, you’ll need to allow traffic from WonderProxy’s IPs through your firewall. Some teams whitelist specific proxy locations to safely grant access to pre-production systems.

To streamline configuration, WonderProxy offers a Proxy Manager that generates connection details for each server and port. It takes care of the setup so you can focus on testing from the right locations without digging through docs or IP lists.

Running Puppeteer through a WonderProxy server

To run Puppeteer through a WonderProxy server, you’ll configure the browser to route traffic through a location-specific proxy. In the example below, the proxy points to Tokyo using jp.wonderproxy.com:11000. That port (11000) is common across most WonderProxy servers, though some configurations may vary.

WonderProxy uses basic authentication, so you’ll need to provide your credentials with page.authenticate() before navigating to any pages. If you skip this step or make the call too late, the connection won’t go through.

Once the proxy and auth are set up, you can visit your target URL and start checking for localized behavior. Look for the right language, correct currency, and any geo-targeted content that should appear based on region.

This setup does more than reflect locale; it provides a genuine, city-level browsing experience that accurately reflects how users interact with your site.

const puppeteer = require('puppeteer');
(async () => {
  const browser = await puppeteer.launch({
    args: [
      '--proxy-server=jp.wonderproxy.com:11000' // Use Tokyo as an example
    ]
  });

  const page = await browser.newPage();
  // Basic auth if needed
  await page.authenticate({
    username: 'yourUsername',
    password: 'yourPassword'
  });

  await page.goto('https://your-site.com');
  // Test localized content here
  await browser.close();
})();

What you can (and can’t) test through WonderProxy

WonderProxy works well in many setups, but not every environment is accessible by default. Here's how different environments stack up when it comes to compatibility:

• Production sites: Usually work out of the box. Since they're already accessible on the public internet, WonderProxy can reach them without any additional setup.
• Staging environments: These an be tested successfully if you allow WonderProxy IP addresses through your firewall. Some teams choose to whitelist specific proxy locations to give limited access to pre-production systems.
• Local development servers: Not accessible via WonderProxy, since they live behind your local network and aren't exposed to the internet. You'll need to deploy them somewhere reachable if you want to test from remote locations.

If you’re planning to test beyond production, set up a staging environment that mirrors the production environment and is accessible to WonderProxy. It's the most reliable way to catch localization issues before anything goes live.

Verifying proxy effectiveness during tests

After your proxy is set up, you should confirm that your browser is routing traffic through the correct location. A quick way to do this is by using WonderSwitcher, the browser extension from WonderProxy. It connects you to a proxy server and can also override the browser’s reported geolocation to match the selected city.

You can also use Puppeteer to capture a screenshot and confirm that localized content is loading correctly. For capturing screenshots, use Page.screenshot().

const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://news.ycombinator.com', {
  waitUntil: 'networkidle2',
});

await page.screenshot({
  path: 'hn.png',
});

await browser.close();

For a little extra confidence, you can add assertions in your script. Check the value of navigator.language, or look for region-specific elements, such as currency symbols or translated labels. These checks help catch silent failures, where the page loads but the default experience remains visible.

Tips for reliable localization tests

Nobody wants an app that stumbles when someone loads it from halfway across the globe. The best way to avoid surprises is to test thoroughly. Combining automation tools with proxy servers lets you create a testing environment that mirrors real user locations. But getting reliable results depends on how you set things up.

Here are a few key practices to help make your localization tests more dependable:

• Test multiple regions: Setting up an automated loop to test across different countries or cities catches quirks like slow load times in far-off places.
• Use consistent test accounts: Using duplicate accounts across tests avoids weird personalization biases that can skew your results.
• Watch CDN behavior: Caching can hide localization issues, so double-check how your content loads without cached data.
• Add visual regression testing: Translations or right-to-left scripts can mess with layouts, so use visual checks to spot design breaks early.

Implementing these practices won’t catch every edge case, but they’ll go a long way toward making your tests more trustworthy. The more realistic your setup, the more confident you can be in what your users will see.

Handling JavaScript-rendered pages and dynamic content

Puppeteer makes it easy to test pages that rely on JavaScript, making it a solid choice for localization testing. While some tools grab static HTML and move on, Puppeteer waits for the full page to load. That includes scripts, styles, and dynamic content. Sites that use client-side rendering benefit most, since key content isn’t available until JavaScript finishes its job.

Before moving on in your test, make sure Puppeteer waits for the elements you care about. Use await page.waitForSelector() to pause until key text or components are visible, especially if translated elements load in later than the rest of the page.

A good rule of thumb: don’t assume content is ready just because the page loaded. Always wait for a specific piece of localized content, like a headline, CTA, or currency display, before running your checks or capturing screenshots.

Troubleshooting common testing issues

Even with everything set up correctly, localization tests can throw you curveballs. Here are a few common issues to keep an eye on and how to handle them:

• Proxy misconfigurations: A typo in the proxy server URL or port can quietly break your test. Double-check the format and make sure you’re using the correct credentials.
• Testing local development by mistake: If your local dev environment isn't publicly accessible, WonderProxy won't be able to reach it. Make sure you're pointing Puppeteer at a production URL that’s accessible over the internet.
• Timeouts from slow international connections: Routing through a proxy adds a bit of latency, especially if you're testing across the globe. If Puppeteer times out, increase your timeout value or add extra wait conditions.
• Debug tip: Log the page’s IP address and user-agent with page.evaluate() or browser dev tools. It’s a quick way to confirm you’re hitting the site from the correct location.

If something looks off, start confirming the basics, such as proxy, authentication, and routing, before digging deeper into the test itself.

Give your localization testing real-world muscle

Once your tests are up and running, put in the effort to make them easier to maintain and scale. Save configurations for proxy settings, test accounts, regions, and assertions to reuse them across projects. Build scripts that loop through multiple cities in a single run and include fallback logic for flaky tests that fail due to network issues rather than actual bugs.

If your test suite includes both staging and production environments, clearly label your test results so that your team can identify differences early. A layout bug that only shows up in staging is still a bug worth fixing.

Localization testing isn’t a one-and-done task. Sites change, copy gets updated, and backend logic shifts. Automating these checks with Puppeteer and WonderProxy enables you to catch regressions quickly before they go unnoticed and quietly go live.