The iMac 24-inch M1 uses a proprietary NVMe controller integrated into the chip

Apple’s M1 iMac doesn’t use a standard M.2 or SATA SSD — the NVMe controller lives inside the M1 chip itself, connected to a proprietary SSD module. That means you can’t swap in an off-the-shelf drive if the original dies. The whole storage system is sealed and non-replaceable, so configure it generously at order time.