Cross-dissolve
One shot fades out while the next fades in over the same few frames, so they overlap. The classic 'time passed' transition.
See it
What it is
A cross-dissolve overlaps two shots and ramps one down in opacity while the other ramps up, so for a moment you see both. Broadcast people call it a mix; audio people call the same move a crossfade. It is the oldest transition in the grammar, and it reads as 'time passed', 'we are drifting', or 'these two things belong together'.
Use it for montages, memory and dream sequences, gentle scene changes, and matching still photos in a documentary sequence. Length carries meaning: 8 to 14 frames feels modern and almost invisible, while a full second or two feels dreamy and old-fashioned. The 1 second default in most editors is slower than most edits want.
Gotcha: dissolves need handles, extra footage past the cut point on both clips. If a clip ends exactly where you cut it, the editor either refuses or quietly shortens your transition, which is why the button sometimes seems broken. Second trap: dissolving between two shots that are both moving turns to mush, so dissolve on stiller frames. And a cross-dissolve is not a dip to black, which goes through black and reads as a harder break.
Ask AI for it
Join these clips with a cross-dissolve: overlap them by 12 frames and ramp the outgoing clip's opacity from 100 to 0 while the incoming clip goes 0 to 100, centered on the cut point, with an ease-in-ease-out curve rather than linear. Trim both clips so there are handles on each side, and dissolve on frames where camera movement is minimal.