SeikisoViewer is a Firefox browser extension designed to enhance the viewing experience of YouTube Live streams by displaying comments in a style reminiscent of Nico Nico Douga. This multimedia tool allows users to customize the display of comments on the video screen, including options for position, speed, and transparency when there are many comments. Additional features include toggling the display of user icons and names, as well as repositioning the comment input area for seamless interaction while watching videos in full-screen mode.

Another notable feature of SeikisoViewer is the time memo function, which enables users to click a memo icon at any moment to save the timestamp of significant scenes. This allows for easy navigation to those moments later during the archived video. For optimal performance, users experiencing issues with comment flow may need to disable any ad-blocking extensions they have installed.