If you have not installed Stow yet, the install guide is here - it covers both macOS and Windows. This article picks up at the first launch.
The setup wizard
On first launch a short wizard walks the choices worth making once: disk access on the Mac, how updates work, the offload log, Wrap, and a pointer to phone alerts. Every step can be skipped, "Set up later" is one click, and everything in it lives in Settings afterwards - the wizard never stands between a card in hand and an offload.
Disk access on the Mac
Stow reads your cards at the disk level - that is how it proves every byte of a copy rather than taking the copy's word for it. macOS calls this Full Disk Access and asks for your say-so once. The wizard's button opens the right Settings pane; drag Stow in, switch it on, and reopen the app. Skip it and Stow will remind you at each launch until it is done, because without it an offload stops mid-flow with "Operation not permitted". Windows needs nothing.
Cards in, drives in
The setup screen is two zones and a few fields:
Cards are what you are copying from - click one in the tray, drop it into the zone, or press + to pick a folder. Destinations are where the copies go, and this is the decision that matters: two separate drives. Stow copies to every destination in one pass, verifies each copy byte for byte, and only calls a card safe to wipe when two verified copies sit on two independent drives. One drive is a copy; two drives is a backup.
The fields above - client, project, date - decide the folder tree, which ends up as <Client>/<Date>_<Project>/<Camera>/<Card> with the card's own structure preserved inside. The line under the fields always shows exactly where the footage will land, and the Folder layout buttons shorten the tree if you do not work with clients.
Press Start
Stow copies, then verifies, then answers plainly: green means every file matches byte for byte on two separate drives and the card is safe to format in the camera; amber means there is only one verified copy, so keep the card; red means something did not verify, with the reason named. The verdict is the product - Stow never softens it.
While it runs, you do not need to watch. Phone alerts can buzz you when the verdict is in, and cards added mid-run join according to your Settings choice.
Stow is free for macOS and Windows. The download is here.