Download One Two Cool!

Name: One Two Cool!
Author: Ersin

By: Ersin Theme

Download One Two Cool! (current and past versions) for Firefox

Latest Version: 3.0 Updated: 9 days ago

Ready to install?

One Two Cool! is available to install from Firefox Add-ons Store and for download from this page.

View source code

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Available versions

You can find the current and older versions of One Two Cool! 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
3.0	XPI · ZIP · Source code	20.01KB	0	2026-07-06

2026-07-06 · 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 One Two Cool! ZIP file.
In Firefox browser, go to about:addons to open Add-ons Manager
Click on ⚙, Install Add-on From File
Select the One Two Cool! ZIP file from step 1. One Two Cool! is now installed on your browser.