Cutting on action is one of the first things taught in editing courses. Films that editors consider classics ignore it regularly.
What the rule actually says
Cut during a physical movement - a door opening, a hand reaching, a head turning - so the edit is masked by motion. The viewer follows the action rather than registering the cut point. Standard continuity editing relies on this heavily.
When editors cut before or after instead
Reaction cuts hold on a face well past the moment action begins in the scene. This creates tension or irony depending on context. The edit is not on the action - it is sitting with the emotional weight before the action resolves. French New Wave editors made this a consistent pattern in the 1960s and it has never disappeared from serious editing practice.
The L-cut and J-cut do something different entirely
Audio from the incoming shot overlaps the outgoing image. The edit is not on action at all - it is on sound rhythm. Most editors use these far more frequently than straight cuts on movement once they have a few years of experience.
- L-cut: outgoing video, incoming audio
- J-cut: incoming audio before incoming video
Neither follows the cut-on-action principle and both are standard technique.