How To Change The User Agent In Chrome And Firefox (2025 Guide)

Changing the user agent allows your browser to pretend it’s running on a different device, operating system, or browser. This is especially useful for:

• Testing how websites display on various platforms

• Accessing region-locked or restricted content

• Debugging layout or performance issues across devices

This guide walks you through the exact steps to change the user agent in Google Chrome and Mozilla Firefox in 2025.

What Is a User Agent?

A user agent string tells websites what browser, operating system, and device you're using. Changing it can affect how websites behave or what version of the site they display.

How to Change User Agent in Chrome

Option 1: Using Chrome Developer Tools

• Open Chrome and go to any webpage

• Press Ctrl + Shift + I (or Cmd + Option + I on Mac) to open Developer Tools

• Click the three-dot menu in the top-right of Developer Tools

• Go to More tools > Network conditions

• Uncheck “Select automatically” under User agent

• Select a preset user agent from the dropdown, or enter a custom string

• Refresh the page to apply the new user agent

Option 2: Using Chrome Extensions

Install an extension like:

• User-Agent Switcher and Manager

These allow one-click switching between different user agents for easier testing.

How to Change User Agent in Firefox

Step-by-Step via about:config

• Open Firefox and type about:config in the address bar

• Accept the warning prompt

• Search for general.useragent.override

• If it doesn’t exist:

  • Right-click → New > String

  • Name it general.useragent.override

• Double-click the entry to add a custom user agent string

• Reload your page — the new user agent is applied globally

Summary of Key Differences

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Frequently Asked Questions (FAQs)

What is the purpose of changing a user agent?

It lets you simulate different browsers or devices — useful for testing how websites behave under various conditions.

Is it safe to change the user agent?

Yes. It doesn’t harm your device or browser and is commonly used by developers and testers.

Can I reset my user agent to default?

Absolutely. In Firefox, reset the config value. In Chrome, close the tab or uncheck the custom setting in Developer Tools.