NAND storage in the new Mac mini models with the M6 and M5 Pro chips is soldered to the logic board, making storage unremovable and preventing aftermarket upgrades. This reverses the removable storage feature found in M4 and M4 Pro models. "Expand Mac mini" previously offered cheaper plug-and-play SSD modules, letting customers save money by buying the 256GB base model and upgrading later—now impossible with the new designs.

Additionally, all new 256GB Mac mini configurations reportedly use a single NAND chip instead of dual 128GB chips, resulting in significantly slower SSD speeds. According to AAPL Ch.'s testing with Blackmagic's Disk Speed Test, the M6 256GB model achieved read speeds of 3,216.8 MB/s and write speeds of 3,000.2 MB/s—roughly half the 6,371.5 MB/s read and 6,577.4 MB/s write speeds of the 512GB model. Users seeking maximum performance should opt for at least 512GB storage.

Notably, even with 256GB, the new Mac mini SSD is meaningfully faster than the previous generation. The M4 256GB model scored only 2,792.5 MB/s read and 2,014.5 MB/s write. Other Mac mini models with M1, M2, and M2 Pro chips also had soldered storage, making the M4/M4 Pro removable storage a rare exception.