Download Header Spy

Name: Header Spy
Author: xbq666

By: xbq666 Add-on

Download Header Spy (current and past versions) for Firefox

Latest Version: 1.2.1 Updated: 4 months ago Removed

Ready to install?

Header Spy is available for download. Be careful when installing it.

View source code

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Available versions

You can find the current and older versions of Header Spy here. You can download the archived versions or inspect their source codes.

As a free user, you can download up to 3 latest versions.

Upgrade to download older versions

Version	Download	Size	Download count	Timestamp
1.2.1	XPI · ZIP · Source code	14.03KB	0	2026-04-15

2026-04-15 · 0 downloads

XPI ZIP Source code

Install XPI file

An XPI file, short for "XPInstall," is a compressed file format used primarily by Mozilla applications, like Firefox and Thunderbird, to distribute and install add-ons or extensions. These files are similar in function to CRX files for Chrome but cater to the Mozilla ecosystem.

Simply drag-and-drop the XPI into Firefox to install the add-on.

Install ZIP file

Download the Header Spy ZIP file.
In Firefox browser, go to about:addons to open Add-ons Manager
Click on ⚙, Install Add-on From File
Select the Header Spy ZIP file from step 1. Header Spy is now installed on your browser.