October 6, 2025

Setting Up User Agents in Chromium for Mobile Inspection

Learn how to configure user agents in Chromium-based browsers to inspect mobile-specific elements, similar to Safari’s functionality.

What you’ll build / learn

In this tutorial, you will learn how to set up specific user agents in Chromium-based browsers, such as Google Chrome or Microsoft Edge. This setup will allow you to simulate mobile devices and inspect mobile-specific elements on web pages. By the end of this guide, you will be able to switch user agents easily, retrieve IDs and classes of elements, and ensure that your web applications function correctly across different devices.

You will also gain insights into the importance of user agents in web development and how they can affect the rendering of websites. This knowledge will empower you to debug and optimise your web applications more effectively, ensuring a better experience for mobile users.

Furthermore, you will explore best practices for using user agents, common pitfalls to avoid, and alternative methods for testing mobile responsiveness. This comprehensive understanding will enhance your development skills and confidence in working with web technologies.

Why it matters

Setting user agents is a crucial skill for web developers, particularly those focused on mobile web applications. Mobile devices have different screen sizes, resolutions, and capabilities compared to desktops. By using specific user agents, developers can see how their applications will appear on various devices, helping to identify layout issues and functionality problems.

Moreover, many websites serve different content based on the user agent. For instance, a site may display a mobile-friendly version or hide certain elements that are not relevant to mobile users. Understanding how to manipulate user agents allows developers to test these variations effectively, ensuring that all users receive an optimal experience.

Additionally, with the rise of mobile internet usage, it is essential for developers to be proactive in ensuring their applications are responsive and accessible. By mastering user agent configuration, developers can stay ahead of potential issues, leading to more robust applications and higher user satisfaction.

Prerequisites

Before diving into the setup process, ensure you have the following prerequisites: a Chromium-based browser installed on your computer, such as Google Chrome or Microsoft Edge. If you do not have one installed, you can download it from the official website.

Familiarity with basic web development concepts, such as HTML, CSS, and JavaScript, will also be beneficial. While you do not need to be an expert, understanding how web pages are structured will help you as you inspect elements and troubleshoot issues.

Additionally, having a basic understanding of the developer tools in your browser will enhance your experience. If you are new to developer tools, consider reviewing introductory resources to familiarise yourself with their layout and functionality before proceeding.

Step-by-step

Open your Chromium-based browser. Ensure it is updated to the latest version for optimal performance and security.
Access the Developer Tools by right-clicking on any web page and selecting ‘Inspect’, or by pressing Ctrl + Shift + I (Windows) or Cmd + Option + I (Mac).
In the Developer Tools panel, locate the three vertical dots in the top right corner and click on them to open the menu.
Select ‘More tools’ from the dropdown menu, then click on ‘Network conditions’. This will open a new panel within the Developer Tools.
In the ‘Network conditions’ panel, uncheck the box that says ‘Use browser default’. This will allow you to manually select a user agent.
Scroll down to the ‘User agent’ section. Here, you will see a list of predefined user agents. You can choose one from the list or enter a custom user agent string.
If you wish to enter a custom user agent, you can find a list of user agent strings online. Copy the desired user agent string and paste it into the input box.
Once you have selected or entered your desired user agent, refresh the web page. The browser will now render the page as if it were being viewed on the selected device.
Inspect the elements on the page to retrieve their IDs and classes as needed. You can do this by hovering over elements in the ‘Elements’ tab of the Developer Tools.
To switch back to the default user agent, repeat steps 1 to 4 and check the ‘Use browser default’ box in the ‘Network conditions’ panel.
Experiment with different user agents to see how your web application behaves across various devices. This will help you identify any issues that may arise on mobile platforms.
Finally, document any findings and adjustments needed for your web application based on your testing with different user agents.

Best practices & security

When setting up user agents, it is essential to follow best practices to ensure accurate testing and security. Always use the latest version of your browser to take advantage of security updates and features. This practice will help protect you from vulnerabilities that could be exploited during testing.

Additionally, when entering custom user agents, ensure that you are using reputable sources for user agent strings. Avoid using unknown or suspicious strings that could lead to unexpected behaviour or security risks. Stick to well-documented user agents from trusted websites.

Moreover, while testing with user agents, remember that this method simulates device behaviour but does not replicate it perfectly. Always complement your testing with real device testing to capture nuances that may not be evident in the browser.

Common pitfalls & troubleshooting

One common pitfall when setting user agents is forgetting to refresh the page after changing the user agent. If you do not refresh, the page may not render correctly according to the new user agent, leading to confusion during testing. Always remember to refresh after making changes.

Another issue may arise from using outdated user agent strings. Some websites may not support older user agents, resulting in incorrect rendering or functionality issues. Ensure that you are using current user agent strings to avoid these problems.

If you encounter unexpected behaviour while testing, double-check that you have correctly selected the user agent and that you have refreshed the page. If issues persist, consider testing on actual devices to compare results and identify discrepancies.

Alternatives & trade-offs

Method	Pros	Cons
Device Emulators	Can simulate various devices accurately.	May require additional setup and resources.
Real Device Testing	Provides the most accurate results.	Can be time-consuming and requires access to multiple devices.
Browser Extensions	Easy to use and often free.	May not support all user agents or devices.
Online Testing Tools	Accessible from anywhere with an internet connection.	Limited control over testing environment.

Each method has its advantages and disadvantages. Device emulators are great for quick testing, but they may not always accurately reflect real-world performance. Real device testing is the gold standard, providing the most reliable results, but it can be impractical for developers with limited access to devices.

Browser extensions offer a user-friendly way to switch user agents but may not cover all scenarios. Online testing tools can be convenient, but they often lack the flexibility needed for thorough testing. Ultimately, the best approach may involve a combination of these methods to ensure comprehensive testing across various platforms.

What the community says

The developer community widely acknowledges the importance of user agents in web development. Many developers share their experiences and tips on forums and social media, highlighting how user agents can significantly impact the testing process. Users often recommend specific user agent strings that have proven effective for different scenarios.

Additionally, there are numerous discussions about the best practices for using user agents, including advice on avoiding common pitfalls. Many developers emphasise the need for thorough testing on actual devices, reinforcing the idea that while user agents are useful, they should not be the sole method of testing.

FAQ

Q: What is a user agent?

A user agent is a string that a web browser sends to a web server to identify itself and provide information about the device and operating system it is running on. This information helps websites tailor their content and functionality based on the user’s device.

Q: How do I find user agent strings?

You can find user agent strings from various online resources, including websites dedicated to listing user agents. These resources often provide updated strings for different devices and browsers, ensuring you have the latest information for testing.

Q: Can I create my own user agent string?

Yes, you can create your own user agent string. However, it is essential to ensure that the string accurately reflects the device and browser you wish to simulate. Using incorrect or misleading user agent strings can lead to unexpected behaviour during testing.

Q: Is it necessary to test on real devices?

While using user agents is helpful, it is crucial to test on real devices to capture nuances that may not be evident in a simulated environment. Real device testing provides the most accurate results and helps identify issues that may only appear in actual usage scenarios.

Q: What should I do if my website does not display correctly on mobile?

If your website does not display correctly on mobile, first check the CSS and HTML for responsive design issues. Use the user agent setup to inspect how the site behaves on different devices, and make adjustments as necessary to improve mobile compatibility.

Q: Are there any risks associated with changing user agents?

Changing user agents is generally safe; however, it is essential to use reputable sources for user agent strings. Avoid using unknown strings that could lead to unexpected behaviour or security risks. Always revert to the default user agent after testing.

Source

For additional information and community discussions, visit the original Reddit post at this link.