Retention spike

Retention graphs mostly slope downwards, so anything that climbs stands out. A spike means people went back over a section, either dragging the scrubber to it or replaying it outright. Common causes are on-screen text that needed longer to read, a figure someone wanted to note down, a quick visual gag, or a demonstration that went past too fast. Read a spike as demand for more of that thing, then look at what happens immediately after it, because a spike sitting right before a cliff usually means viewers got what they came for and left.