The newest SSD only Macs use PCIe-based flash drives and are not compatible with third party drives that use a SATA interface. I just checked OWC and Crucial and neither offered upgrade or replacement SSDs compatible with SSD only Macs later than 2015 models. Both offer SSDs to replace SATA HDs in Macs so equipped. I don't know about the SSD portion of Fusion drives in more recent iMacs but if the SSD is SATA it could be upgraded to a larger SSD and certainly the HD portion could be replaced with a third party SSD.

The reason Apple has moved away from the SATA interface for SSDs is the SATA bus is significantly slower than the SSD and becomes a drive I/O choke point.


If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein