The video progress bar makes it easy to check where you left off the last time you watched a video. When you leave a video without finishing it, a bar under the video thumbnail shows you where you left off. When you play the video again, it will restart from where you were.
The progress bar is available when you’re signed in to your Google Account on TV, your computer, or the YouTube mobile apps.
Note: Clearing your watch history will also clear all progress bars.
When you select a partially watched video, the video will usually resume from where you left off. There are cases where the video won’t restart from where you left off, like when the video is mostly complete.