Your Mac does not checksum your footage

It is easy to assume a modern drive looks after your files, and that the system would notice if a clip went bad. On a stock Mac or PC, it would not.

What APFS actually protects

APFS, the filesystem on every current Mac, checksums its own metadata: the records that track where files live. It does not checksum the file data itself. A flipped bit inside a clip is invisible to the filesystem. Default Windows volumes (NTFS) do not checksum file data either.

So nothing on a normal Mac or PC is watching your footage for silent corruption. The copy lands, the size looks right, and a bad block can sit there unnoticed until someone opens the file in the edit.

The drive will not tell you the clip went bad.

The filesystems that do check

Some filesystems checksum every block of data and verify it on every read:

• ZFS and Btrfs checksum all data and can self-heal from a good copy. They live on Linux and NAS boxes (TrueNAS and similar), not natively on macOS or Windows.
• Windows ReFS has integrity streams, but they are off by default and limited on regular Windows machines.
• Enterprise drives can carry end-to-end protection (T10-PI), but that is SAS and NVMe gear in servers, not the SSD in your bag.

Useful to know, but none of it is running on the working drive a shooter offloads to.

So what proves the copy

On the hardware you actually use, the only thing that confirms a clip copied intact is a tool that reads it back and checks it. That is an application doing the work the filesystem does not. It reads every file off the destination, hashes it, and compares it to the source.