A line in the artwork pointing to the artist's Bilibili account.
Prevalent on bilibili videos in either of the 4 corner of the video, mostly top right or left with the format of "<username>bilibili". Most videos have the username visible by default, while some didn't mostly being company channel or similar. You can download Bilibili video without their Bilibili Watermark using bbdown instead of the standard yt-dlp, though only works on select few videos
Note:On May 14th 2026 bbdown repo was archived leaving no further support due to unknown reason so the tool might be unusable in the near future