Cooldown



A cooldown is a period of wait time before a spell, ability, or item power can be used again.

Mechanics
Usually, a skill will be on cooldown if the skill was activated and the cast time of the skill has passed. For instance, Sand King's Epicenter will instantly go on cooldown when activated, since it has no cast time. If the hero is interrupted before the channel time is over, the spell does nothing, and the cooldown and mana is wasted. On the other hand, Sniper's Assassinate and Shadow Fiend's Requiem of Souls have long cast times, and they will not go on cooldown before the cast time is over. Spirit Breaker's Charge of Darkness is an exception to the usual rule; it goes on cooldown once the charge ends or is canceled, not upon cast.

If a hero has several versions of the same item, all versions will be on cooldown upon activating one of them. For instance, all Dagons are in the same cooldown group.

Some abilities or items have multiple cooldowns, using a different duration if their conditions are met. For example 's cooldown is 4 seconds when cast on a tree, but 14 when on units. 's cooldown is 0, but only when successfully killing a hero.

Many abilities have reduced cooldown when leveled up. If an ability is on cooldown and it is leveled up, the current wait time will not be affected at all.

Some abilities have charges and a charge replenish time instead of the usual cooldown. For instance, Sniper's Shrapnel has 3 charges and a 55 seconds replenish time for each charge.

Cooldown manipulation
Several abilities and items are able to manipulate cooldowns of abilities and items. These include cooldown reductions, which can only occur when the spell is off cooldown first, or cooldown resetting.

Percentage-based cooldown reductions and increases stack multiplicatively with each other. Flat reductions and increases fully stack as well. If both are combined, flat changes are added before percentage changes are. This means, when having percentage cooldown reduction and a flat reduction, the flat reduction is applied first, and then the percentage based change is applied.

Final cooldown formula:


 * Final cooldown = (Base cooldown + sum of all flat increases - sum of all flat reductions) × (1 + first percentage increase) × (1 + second percentage increase) × (1 - first percentage reduction) × (1 - second percentage reduction)

Charges
Some abilities use the ability charge mechanic, instead of cooldowns. These abilities have a set number of charges on them, which replenish over time. Instead of going on cooldown, these abilities use up one charge per cast. This means when having multiple charges, they can be cast quickly in succession, but cannot be used when having no charges left. Each charge takes a certain time to replenish. Multiple charges of a spell do not replenish at the same time, they recharge one after another.

Charge-based abilities will appear to be on cooldown when using the last charge. This "cooldown" however is only to visualise when the next charge is going to be ready again.

The replenish time of charges can be affected by the cooldown reductions of and Arcane Rune.

Charge-based abilities
The following abilities use the charge system: