TRIM
also: TRIM command, ATA TRIM, discard
TRIM is a command that tells solid-state drives (SSDs) which data blocks are no longer in use, allowing the drive to reclaim and optimize storage space.
TRIM is a set of ATA commands that communicate between the operating system and an SSD to identify which data blocks have been deleted or are no longer needed. Without TRIM, SSDs can become fragmented and slow because the drive doesn't know which blocks are safe to overwrite.
When you delete a file on a traditional hard drive, the OS simply marks it as deleted but leaves the data intact. With SSDs, this approach causes performance degradation because the drive must erase blocks before writing new data. TRIM allows the OS to proactively inform the SSD: "this data is gone, you can safely erase it when idle."
On Linux, TRIM can be enabled automatically (continuous or periodic) or triggered manually. For example, fstrim / immediately trims the root filesystem. Many Linux distributions enable TRIM by default for mounted SSDs using systemd timers or cron jobs.