TRIM is a feature supported by modern solid state drives (SSDs) that helps improve drive performance. The word "TRIM" is typically capitalized, though it is not an acronym. Instead, TRIM is a command that the operating system uses to allocate free space on an SSD.

When you delete a file on an SSD, the data is often not deleted immediately, but instead is marked for deletion. This prevents certain areas of the flash memory from being written and erased too frequently, which can degrade the SSD's performance over time. However, it also causes many "pages" of free space to be inaccessible, since they are pending deletion. Once enough pages are marked for deletion, the TRIM command performs a "garbage collection" operation. This action deletes large "blocks" of data all at once, allocating free space on the drive.

In order for TRIM to work, it must be supported by a device's hardware and software. This includes the 1) SSD, 2) drive controller, and 3) operating system. Nearly all SSDs made in 2012 or later include TRIM support and therefore most SSD controllers manufactured in 2012 or later support TRIM as well. Windows 7 and later and Mac OS X 10.6.8 and later support TRIM at the file system level. However, in some cases it may be necessary to manually configure TRIM, such as when you install a third party SSD.

NOTE: In Windows 7, you can check if TRIM is enabled by opening the command prompt and typing the following command:

fsutil behavior query DisableDeleteNotify

If the result is "0," TRIM is configured correctly. If the result is "1," TRIM is not active. To enable TRIM in Windows 7, you can type the following command:

fsutil behavior set DisableDeleteNotify 0

Updated August 7, 2013 by Per C.

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