Swift Sneak

Swift Sneak is a very rare armor enchantment in Minecraft 1.21. Swift Sneak removes most of the speed penalty for crouching, letting you sneak around at a brisk pace instead of the usual slow shuffle.

Its opening level already delivers a noticeable boost — Sneaking speed is 45% of walking speed (up from 30%) — and it climbs from there to a maximum of level 3 (III) on your leggings.

Swift Sneak tops out at level 3, shown as III on the leggings, and the gap between the levels is where the enchantment's character really lives.

Each of its three levels raises your sneaking speed: from the default 30% of walking speed up to about 45%, 60% and finally 75% of full speed at Swift Sneak III. It applies while you crouch and is worn on the leggings slot.

Swift Sneak fits exactly one item — the leggings — and nothing else will accept it, so it is a dedicated leggings enchantment through and through.

Swift Sneak has no exclusivity conflicts at all, so you can layer it onto a leggings alongside every other enchantment that leggings accepts without having to give anything up.

Swift Sneak is a treasure enchantment, which means an enchanting table will never produce it. Your only routes are ancient city loot chest, after which you combine the book onto your leggings with an anvil.