Unbreaking

Unbreaking is an uncommon general-purpose enchantment in Minecraft 1.21. Unbreaking makes gear last longer by giving each use a chance to skip consuming any durability, so an item effectively survives far more actions before it breaks.

Its opening level already delivers a noticeable boost — ~50% chance to not lose durability (tools), ~60% for armor — and it climbs from there to a maximum of level 3 (III) on almost any piece of gear.

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

For tools the chance to save durability is 100 divided by (level + 1), so Unbreaking III roughly quadruples a tool's working life. Armor uses a more generous formula, saving durability about 80% of the time at level III, because armor is hit so often.

Unbreaking is about as universal as enchantments come — it goes on sword, pickaxe, axe, shovel, hoe, bow, crossbow, trident, fishing rod, helmet, chestplate, leggings, boots, elytra and mace, which is to say nearly every durable item you own can run it, making it a default consideration on any new piece of gear.

Unbreaking has no exclusivity conflicts at all, so you can layer it onto an item alongside every other enchantment that item accepts without having to give anything up.

Unbreaking can be rolled directly at an enchanting table, where reaching its top level of III on any tool, weapon or armor piece generally wants a fully bookshelf-powered table at roughly level 5. Should the table prove stingy with Unbreaking, you can instead source the book from loot chest and villager trading and anvil it on.

Its selection weight of 5 makes Unbreaking an uncommon roll: it appears with middling frequency when enchanting any tool, weapon or armor piece — common enough to plan around, but not guaranteed on any given roll.