Thumb-Zone Overlay is a free Chrome extension developed by appstrafficlab. It falls under the category of Browsers and specifically belongs to the Add-ons & Tools subcategory.

This tool is designed to help developers check if their designs are user-friendly and intuitive on mobile devices. It provides insights into how users interact with their designs and ensures that important elements are easily accessible.

Thumb-Zone Overlay currently supports two device sizes: iPhone 5 and iPhone 6 Plus. Developers can overlay a CSS layer onto their Chrome tab, creating a heatmap that visually displays areas that users can easily reach, areas that require more effort, and areas that are difficult to access.

With Thumb-Zone Overlay, developers can optimize their designs to enhance the user experience and improve usability on mobile devices. More device sizes are expected to be added in the future, making this tool even more versatile for design testing.