Placebo

"Alone, this mod does nothing but register itself as a mod, hence the name."

- -The mod's CurseForge page

Placebo is a mod by Shadows_of_Fire which replaces all shapeless recipes with a version that matches faster to improve performance. This setting can be disabled if desired, but defaults to true in versions 1.5.1 and above.

In earlier versions, the mod did nothing except register itself as a mod.