How to Modify Headers in Mozilla Firefox

When you visit a website, your web browser sends some information about your web browser and operating system in order for the web server to send the relevant information. For example, if you visit a website using your mobile device (like your smart phone), then it will tell the web server about your using a mobile web browser and then the web server will send the mobile version of the website automatically. Similarly, on a Windows PC, you would see the desktop version of the website because the web server is sent information about your web browser type. However, you can modify the data related to your web browser being sent to the web servers using the Modify Headers extension in Firefox so that to have the web server act as you desire it to act.

The Modify Headers extension does exactly what the User Agent Switcher does for the most part. But it also extends beyond the basic functionality of spoofing the user agent strings and allows you to add many different headers that you want to modify. This can be very useful for web developers who have to check for different header types and their different header values.

After the installation of the Modify Headers extension in Firefox, you can see a new button in the toolbar. You can click on it to pull down a menu that allows you to start and stop it or change the various settings.

Modify Headers for Firefox

In the Modify Headers extension interface, you can add a new header, delete a header or edit its value. When adding a new header, you have to specify the header name, its value and a description for it. If you are going to add the user-agent header, then you can find the values on After adding a new header, you can start the Modify Headers extension by clicking on the Start button in the toolbar or in the Modify Headers extension interface window. Similarly, you can click on the Stop button to stop the extension from modifying the headers.

Modify Headers for Firefox

Verdict: The Modify Headers extension is a fast, safe and quick way to tinker with the browser headers in Mozilla Firefox. You can add and modify all types of headers and their values in it. The extension can be easily toggled on or off at the click of a button.

You can download and install the Modify Headers extension for Firefox from