YouTube Refined: Improve's YouTube UI is a Chrome extension that updates the desktop YouTube UI with rounded corners and various enhancements. This extension focuses on refining and enhancing the user interface of YouTube without altering any functionality. The UI tweaks are designed to work seamlessly in both light and dark modes.

One of the notable UI tweaks is the increased spacing between videos in the subscriptions section, making it easier to navigate through the content. Additionally, a hover animation has been added to each video thumbnail, providing a visually appealing and interactive experience. The video player itself now sports rounded corners and the action buttons have increased roundness.

In the comments section, clear separation has been implemented between each comment, with a faint border and increased padding. The reply chain within each comment also has distinct separation, ensuring a more organized and visually pleasing layout.

Related videos now feature a hover animation with a slight slide-out effect. All thumbnails have rounded corners and the progress indicator bar of unfinished videos has been made slightly transparent. Previously watched videos are now clearly labeled with a background color and a "CONTINUE WATCHING" label.

Various other UI tweaks have been made throughout the extension, including rounded corners for the user menu, a reduced width for the search button, and increased spacing between menu items.

Overall, YouTube Refined: Improve's YouTube UI provides a polished and enhanced desktop experience for YouTube users, focusing on UI improvements without altering the core functionality of the platform.