Cooldown

For a similar mechanic in Diablo II, see Casting Delay.

Cooldown is a property of some powers in Diablo III and subsequent games, primarily character skills, which prevents it from being activated again until a set time has passed. The concept was first introduced as Casting Delay in Diablo II, but that system did not interact with any other game mechanics. Certain item powers and Monster Skills also have cooldowns.

Cooldown Reduction (CDR) is a percentage-based character stat which reduces the length of skill cooldowns, available from many sources. It is an important stat for some builds, allowing more frequent or even continuous use of some skills.

Skills

Active skills with cooldowns start a timer when used (a few instead start the timer after their effects end), as do charge-based skills that are not already recharging. Until the timer expires, attempting to re-use a cooldown skill simply does nothing; the same is true for skills with no charges remaining. The skill is said to be "on cooldown" during this time. For charge-based skills (e.g. Dashing Strike or Revenge), when the timer expires for one recharge period, a charge is restored, and the next recharge period begins immediately if the maximum has not been reached. Recharging benefits fully from Cooldown Reduction.

Cooldown time is visually indicated by a pie chart / clock-style shaded area on the skill icon in the action bar. When a skill is used, the icon becomes fully gray, indicating the cooldown has just begun. Then an increasingly large angle becomes uncovered as time passes, progressing clockwise. The shading turns from gray to orange as the cooldown approaches completion. When it finishes or is reset, the button briefly flashes to indicate the skill is ready for use again. Longer cooldowns move slowly through the 360 degree rotation, while short ones move quickly.

Cooldown skills range from short-cooldown utilities to attacks with a massive impact on the battlefield that may serve as centerpieces or "finishing moves" to a fight. Some have cooldowns of just a few seconds, while the most powerful may go up to 60, 90, 120, or even 180 seconds. Cooldowns longer than that are very rare.

Cooldowns are one of two major limitations skills may be designed with to avoid them being over- or underpowered; the other is its resource cost. Some skills have both limitations, while others such as Diablo III Primary Skills have neither, and can therefore be used as much as Attack Speed allows, but have correspondingly low power.

Some skills have durations of effect. Those that strongly empower the character, such as Archon or Wrath of the Berserker, are designed with cooldown timers longer than durations. This means the character cannot be empowered all the time by re-using the skill before the duration expires by default, but this is possible with high enough Cooldown Reduction. On the other hand, some skills instead do not start cooling down until their effects have ended, generally skills that grant immunity to damage, like Serenity or Falling Sword, or make it difficult to be targeted by enemies, like Smoke Screen or Spirit Walk. This prevents characters from achieving permanent immunity with high Cooldown Reduction - they must always wait some time before the the effect can be reused.

Skills like Unstable Anomaly, which trigger automatically and have exploitable effects like cancelling death, are designed with hard limits to how frequently they can take effect. While the concept is similar to other cooldowns, such skills do not use regular cooldown mechanics, and do not benefit from Cooldown Reduction or other interactions. They usually show a debuff icon on the screen after they have activated. Only death cancels this restriction.

Follower active skills all have cooldowns (and do not use resources). However, none of them benefit from normal Cooldown Reduction, with the exception of Kormac's Heal skill. The AI will generally use the skills shortly after they are off cooldown, if appropriate for the current circumstances.

Mechanics

Cooldown management is a vital part of gameplay, although some cooldown-independent builds exist as well.

There are two quantities involved when using a cooldown skill, both of which can be updated by effects during gameplay:

• The skill's overall cooldown time, generally found by reducing the base cooldown of the Skill Rune by the character's current Cooldown Reduction stat. The moment the skill is used, the cooldown timer starts equal to overall cooldown time. Changes to this value, such as by gaining or losing Cooldown Reduction, are not obvious visually, since the icon always starts fully gray regardless of cooldown length, but players will notice their next use of the skill takes a different amount of time to come off cooldown than the previous use, and may be able to see the progress indicator is moving through the circle at a different rate.
• The current time remaining on the cooldown period, which generally decreases with the natural passage of time. Thus, if no other effects are involved, the actual duration the skill is on cooldown is equal to its overall cooldown time at the moment the skill was activated. Special powers that decrease the current cooldown's time create an abrupt jump in the progress of the rotating cooldown indicator, although this can be harder to notice for long cooldowns.

Naturally, if the current time remaining is reduced by a special power, it does not affect the overall cooldown period; the next use of the skill still starts with a duration equal to the skill's overall cooldown. More surprising is the converse: If the overall cooldown time is modified while the skill is already on cooldown, the current time remaining is not modified - even if the new overall cooldown time is less than the current time remaining!

A skill cannot be replaced by another in the action bar while it is cooling down, preventing rotation through multiple high-cooldown skills in a single action bar slot. Swapping loadouts with the Armory bypasses this restriction.

All cooldowns are reset immediately when a Greater Rift is started.

Cooldowns continue to recharge even while a character is dead.

Interactions

Many effects and character statistics can change skill cooldown times. None of these are included in the "estimated effectiveness stats" on the Diablo III Character Screen (Damage, Toughness, and Recovery), but they can have a huge impact nonetheless.

Each skill has a set base cooldown time, possibly 0. Some Skill Runes change this base, for example Archon's Pure Power rune. Some Runes remove the cooldown entirely (often adding a resource cost in its place), or add one that was not present in the un-runed version. Certain Legendary Item unique powers make similar changes, such as Aether Walker (for Teleport). And a few passive skills may make flat reductions to specific skills' base cooldowns, like Boon of Bul-Kathos. All further interactions are relative to this base cooldown period.

Cooldown Reduction

Foremost among modifications is Cooldown Reduction (CDR), a percentage that is removed from the overall cooldown time of all skills. This stat is listed in the Character Screen's secondary stats panel under "Offense", although many defensive skills benefit from CDR as well. CDR applies the moment a skill is activated, so subsequent changes to the stat have no effect on a skill that has already started cooling down.

Aside from the normal benefits of Cooldown Reduction, Captain Crimson's Trimmings also grants a direct bonus to damage equal to a character's Cooldown Reduction stat.

Sources of Cooldown Reduction in Diablo III:

• Passive skills like Evocation and Beacon of Ytar.
• Item set bonuses like Captain Crimson's Trimmings.
• A Diamond in the helm socket reduces all cooldowns by up to 12.5%.
  • Leoric's Crown doubles this bonus, to up to 25%.
  • The head-socketed Soul Shards in some seasons have slightly better bonuses than Perfect Royal Diamonds.
• "Reduces cooldown of all skills by X%" can appear as a primary attribute on gloves, amulets, rings, pauldrons, off-hand items (up to 8%) or weapons (up to 10%).
  • Different items with this attribute are counted as completely separate sources of CDR; the percentages are not simply added together (see below).
• The Gogok of Swiftness Legendary Gem at level 25 or above grants up to 15% CDR based on a stacking effect which must be actively maintained.

Multiple sources of Cooldown Reduction apply sequentially. For example, a 20% CDR passive results in a cooldown length 80% of the original. If a 10% CDR item is also equipped, it reduces 10% of that 80% (8% of the original cooldown time), resulting in a final cooldown time 72% as long as the original. This can also be thought of as multiplicative stacking of CDR effects, if they are stated in terms of the relative remaining cooldown times: .8 * .9 = .72, with the same example. Note that regardless of the order of the effects or how many there are, the result will be the same. This is a form of diminishing returns for Cooldown Reduction (e.g. a new source is only half as effective if the character already has 50% CDR), and it is impossible to achieve 100% CDR through combinations of smaller effects.

There are some builds focusing on keeping lower cooldowns for long-recharging spells, but the cap for most classes is around 72-75% (84.5-88.5% with Leoric's Crown).

Other reductions

A variety of powers and effects can reduce or interact with cooldowns without an associated character stat.

These effects apply percentage reductions applied sequentially which take effect the moment a skill is used, just like the Cooldown Reduction stat:

• Empowered Shrine and Channeling Pylon reduce all cooldowns by half and by three quarters, respectively, for their duration. The Pylon also resets the cooldowns that are already active.
• Some Legendary Items or passive skills may reduce cooldowns of one or more specific skills, like Gesture of Orpheus or Lord Commander.

These effects reduce current cooldowns of skills that have already been activated:

• Item powers which reduce some or all skills' current cooldowns by a set amount per trigger, including Obsidian Ring of the Zodiac, Messerschmidt's Reaver, and Armor of Akkhan's 4 piece bonus.
  • Trag'Oul Coils was formerly known for a strong version of this effect, but has been redesigned.
• Passive skills which do the same, like Grave Injustice.
  • Critical Mass proved so effective that it has been removed from the game altogether.
• The "Runic Circle of Creation" from the Mother seal of the Altar of Rites (and the original "Triune Circle of Creation" from Season 18) reduces the remaining time of all skills on cooldown by 1 second, each second the character is in the circle. Overall, this doubles cooldown progression rate.
• Skills which reduce the cooldowns of other skills when activated, such as Akarat's Champion with Rally rune.
• Passive effects which reset existing cooldowns, instantly removing them regardless of how much time remains, for instance Illusionist.
• Skills which regain charges or reset cooldowns based on a trigger condition, as with Revenge.

In-Geom reduces all skill cooldowns by a set amount when it triggers, similar (but stronger) than the Obsidian Ring above. In addition, for a short duration, it modifies all skills with a flat subtraction to the base cooldown period. Like regular CDR, this deduction applies at the moment the skill is used. This can potentially set some cooldowns to 0, but if not, percentage-based Cooldown Reduction is applied after the In-Geom benefit.

Followers do not benefit from regular cooldown reduction bonuses on items, with the exception of Kormac's Heal skill. However, each follower has a Legendary trinket that halves their skills' cooldowns: Vadim's Surge, Slipka's Letter Opener, and Hillenbrand's Training Sword.

Items and other cooldowns

Cooldowns of skills triggered by items are usually separate from cooldowns of identical skills wielded by the player, if any.

Cooldowns of item special effects (such as Firebird's Finery set bonus) are not affected by the cooldown reduction, unless specifically stated otherwise. Moreover, cooldowns of all passive skills that prevent a hero from dying (Unstable Anomaly, Near Death Experience, Spirit Vessel etc) cannot be reduced by any means possible.

The potion cooldown of 30 seconds may not be reduced by the cooldown reduction; the only ability in game able to reduce it is the Blood Flask Necromancer skill rune.