This app promises to run "fstrim" without root but I am not sure if it works

Question

I am not sure if this app works. Can someone please help me? My phone is new and in its warranty period so I can't root it yet. I tried this app but I am not sure if it actually did something. Unlike the other famous app on the PlayStore for fstrim, it doesn't require root access which is quite incredible.

Answer 1

I highly doubt it. I use an app called Trimmer which requires root to trim /cache, /data, /system. I installed this app & ran only selecting cache, but it shower trimeed cache & data. I ran a logcat, did not catch anything. So most probably it is a snake oil or at best it clears your cache.

Answer 2

AFAIK, only apps running as root (UID 0) ⁽¹⁾ or system (UID 1000) ⁽²⁾ or with android.permission.MOUNT_UNMOUNT_FILESYSTEMS ⁽³⁾ can do fstrim. But third party apps can neither get UID 0/1000 (without rooting phone), nor the said permission is for third party apps ⁽⁴⁾.

Also manually sending FITRIM ioctl with fstrim command requires at least capability SYS_ADMIN ⁽⁵⁾, which is almost root if not full root.

The app you have mentioned asks for permissions CLEAR_APP_CACHE (delete all apps cache data) and KILL_BACKGROUND_PROCESSES (close other apps). So it's quite evident what it must be doing to give a feel of lag-free experience.

PS: You don't need to run fstrim manually in most cases, OS can handle this. See this answer.