Where to keep recordings

Any folder this Mac can write to will do, but not every folder behaves the same.

Avoid iCloud Drive and other syncing folders. macOS is free to remove the local copy of a file in iCloud Drive whenever it wants space back, leaving a placeholder that has to be downloaded again. A clip that is evicted is still listed and still playable eventually, but it is no longer on this Mac — which is the one thing a recording of an intrusion needs to be. Syncing also uploads every clip, which for continuous recording is a great deal of traffic.

An external drive is fine, with one caveat: if it is unmounted or asleep when a recording starts, there is nowhere to write. OdinCam reports that rather than failing quietly, but the event is still missed.

The default folder in Movies is a plain local folder, which is why it is the default.

Several cameras can share one folder, such as a network drive. Each clip's name includes its camera's name, so they never collide, and each camera only fetches, counts and deletes its own clips: one camera's size limit never removes another's recordings. Clips recorded before names were added belong to every camera, as before.