Since Apple first offered Macs with solid-state drives (SSDs), they have added support for TRIM, a method that helps the operating system free up space. It also helps extend the life of the drive and promote efficient operation.

The TRIM command helps the operating system clean up data in storage blocks that are no longer needed. This optimizes the write performance of an SSD by leaving more blocks of data free to write to. It also prevents the SSD from being so aggressive in cleaning up after itself that it causes wear and tear on the memory chips. In this way, it prevents premature failure.

TRIM is supported in OS X Lion (10.7) and later for all drives, but it is enabled by default only on SSDs shipped by Apple. It's unclear why Apple has limited TRIM support in this way, but the prevailing consensus is that TRIM implementation is manufacturer-dependent, and each manufacturer uses a different TRIM methodology. For this reason, Apple has chosen to enable TRIM only on SSDs it has certified.

A few third-party utilities can enable TRIM for SSDs not supplied by Apple, including TRIM Enabler. These utilities take advantage of Apple's built-in TRIM support, while removing the operating system's ability to check if the SSD is on Apple's list of approved manufacturers.