HCOS is a free Chrome add-on developed by SiyiLee. This add-on is designed to hide the historical search suggestions that appear in the address bar of the new tab page. The main purpose of this extension is to remove the Google search records that pop up after the cursor is focused in the address bar.

One of the key features of HCOS is the ability to add a custom website. By opening the extension options page, users can add a custom URL prefix to the page, allowing for a more personalized browsing experience.

With HCOS, users can enjoy a clutter-free address bar and have more control over their browsing privacy. This add-on is a useful tool for those who want to keep their search history private and customize their browsing experience.

Please note that HCOS is only available for the Chrome platform. It falls under the category of Browsers and the subcategory of Add-ons & Tools.