Danmaku (弹幕) is Bilibili's on-video scrolling commentary — comment text bound to a specific second of the video, which no other platform has. With this on, each video also returns one type: danmaku row with danmakuFetched, danmakuUniqueSenders, danmakuPerMinute, the peak minute and its count, first/last timestamps, and an evenly-spread text sample across the whole video. What it is for: second-by-second audience reaction on an ad or a launch, and creator vetting — danmaku-per-minute beats view count as an engagement signal because a danmaku costs the viewer effort. Measured: a single video carries ~3,000 danmaku (3,415 on one test). Cost is predictable: this adds ONE row per video, not one per danmaku. Off by default. Billing: each danmaku row is its own danmaku-profile event at $0.05 — 2.5x a normal $0.02 row — because it fetches and reduces ~3,000 danmaku per video. Profiling 200 videos costs $10. Off by default.