AltNumber is a Firefox extension designed to enhance tab navigation by introducing keyboard shortcuts for switching tabs efficiently. Users can easily switch to specific tabs using the Alt key combined with a number, where Alt+1 takes you to the first tab, Alt+2 to the second, and so forth, up to Alt+9 for the last tab. This functionality mirrors the tab-switching shortcuts familiar to Linux users, making it a seamless addition for those who often navigate multiple tabs.

As a subscription-based personalization tool, AltNumber aims to streamline the browsing experience by reducing reliance on the mouse for tab management. This extension is particularly useful for users who frequently work with numerous tabs open at once, allowing for quicker access and improved workflow. The straightforward implementation of keyboard shortcuts makes it an intuitive choice for enhancing productivity while using Firefox.