Interrupt

Interruption refers to slowing or stopping a target's spellcasting.

There are two main types of interruption:
 * Interruption caused by damage (also known as pushback)
 * Interruption caused by specific abilities

Interruption caused by damage (pushback)
Whenever a damaging spell or ability hits a caster mid-cast, the cast time will be set back by a given amount, slowing and delaying the cast. In contrast, pushback foreshortens channelled spells, causing them to end earlier without having had their full effect, but does not slow or delay them. Pushback therefore reduces the speed of cast-time spells, while reducing the mana efficiency of channelled spells.

In general any melee attack (be it a normal or a special attack) or direct damage spell will cause interruption. Damage over Time spells and most channelled spells will not cause interruption. The only channeled spell which does is Arcane Missiles.


 * When casting a spell: The first and second hit will add .5 secs each to the cast time. All hits after the second will have no effect.


 * When channeling a spell: The first and second hit reduce current duration by 25% of total duration each. All hits after the second will have no effect.

Interruption caused by specific abilities
Numerous abilities can be used to immediately interrupt spellcasting. When a player's spellcasting is interrupted, their cast is immediately cancelled, and their cast time bar will turn red and say "Interrupted". Cast-time spells that are interrupted mid-cast will not consume mana, and any global cooldown will be cancelled, allowing the caster to immediately cast another spell.

Interrupt abilities
Abilities that specifically interrupt spell-casting are known as "interrupts". These abilities generally do not cause damage, are instant cast and unaffected by the global cooldown, allowing their use at any time. If a spell is successfully interrupted, they also cause a counterspell effect, preventing the target from casting any spell from the same school as the interrupted spell for a number of seconds. Counterspell effects provide no visual debuff and cannot be dispelled. Interrupts are available to all classes and specs, with the exception of Holy and Discipline priests.

Interruption can be prevented by certain abilities, such as Unending Resolve.

Silence effects and many forms of crowd control such as Fear effects, Horrify effects, Stuns, Incapacitate effects and Polymorph/Hex can also be used to interrupt a target's cast. Proper use of these abilities can be very effective for interrupting spellcasting, although they lack the counterspell effect of true interrupts.

Some abilities incorporate both silence effects and interrupts. This allows for interrupt functionality against PvE targets such as bosses that are immune to silence effects.

The following is a list of abilities that specifically interrupt spellcasting. Note that a few of these abilities only provide interrupts for non-player targets. All of these abilities cause a counterspell effect, although the duration is variable. The below abilities are also all instant cast, and are unaffected by the global cooldown.

Pummel, Kick, Rebuke, Mind Freeze and Spear Hand Strike are all fairly similar abilities; all require melee range, have a 15-second cooldown and lock the school for 4 or 5 seconds. Skull Bash is very similar, but benefits from a 13-yard range and also increases the victim's mana costs. Counter Shot, Counterspell and Spell Lock are likewise very similar spells, although durations vary, and Spell Lock has the advantage of being usable at very long range and while the Warlock is stunned/silenced/incapacitated, since it is cast by the Felhunter pet. Kick has the best overall counterspell/cooldown ratio, improved further by Glyph of Kick, while Wind Shear is available the most frequently, being the interrupt with the shortest cooldown (and duration).

Tips and tactics

 * Instant cast spells cannot be interrupted, as they have no cast time and as such cannot be affected during casting. Any normally cast spell or channeled spell can be interrupted, though. Other effects such as silences and stuns can be used to prevent instant casts.


 * When in danger of being interrupted, healers can protect themselves and those under their care from the effects of interrupts by using their instant heals (and absorption effects such as Power Word: Shield) before using cast-time heals. In this way, even if their cast-time heal is immediately interrupted, the target will already have received some healing/protection.


 * Choosing which spell to interrupt is key. Interrupting as often as possible may result in a significant reduction in your target's effectiveness, but saving interrupts for critical casts can be even more devastating. In general, when interrupting healers, try to wait for a critical moment to make the most of the interrupt. Damage-dealers are often better handled by simply interrupting them as frequently as possible, steadily reducing their damage output. Alternatively, wait for your opponent to pop some of their damage-boosting cooldowns before interrupting them, causing them to waste the effects.


 * Some specializations are far more vulnerable to school lockouts than others. Saving interrupts for spells belonging to the target's main school usually allows for the maximum possible disruption.


 * Some players will 'fake-cast' - begin casting a non-critical spell belonging to a secondary school in order to fool enemies into using their interrupts. If the enemy uses their interrupt, the player is then free to cast from their main school while the enemy's interrupt is on cooldown. When facing more experienced opponents, casters may start casting a spell from their primary school before quickly switching to one from a secondary school, in the hope that their opponent will react a moment too late and accidentally interrupt the second spell, so leaving the caster free to cast from their main school.


 * When locked-out of your main school, make the most of the time by using your other abilities. Even if the benefit is small, it is generally preferable to simply waiting for the lock-out to expire. Players who have just interrupted you will also probably be unable to interrupt you again for at least 10 seconds.


 * Some abilities are multi-school (such as Frostfire Bolt, or Mind Spike), meaning they belong to two or more different schools of magic. As long as any of the spell's schools is available, the player will be able to cast the spell. This makes multi-school spells extremely hard to lock down, and means they will almost always be available for players to cast when one of their schools is locked. In addition, some multi-school spells such as Divine Star belong to schools that are not used by any of the class's other spells. When these spells are instant cast, this means that it is not possible for that spell to be locked down.


 * Interrupts have varying range requirements. Being aware of these requirements and the distance and locations of targets can be critical for interrupting casts in time.


 * When interrupts are unavailable, other abilities such as silence effects and stuns can be used to prevent the target from casting.


 * Like silence effects, interrupts can be used in PvE to draw caster mobs into melee range, as casters who are prevented from casting will run toward their current target.


 * Timing is critical when using interrupts. If used against a target that is not currently casting, the counterspell effect will not be applied, and the interrupt will be wasted.


 * Learn each class's interrupt capabilities. Learn which require melee range to interrupt, and which have additional silences and ranged stun effects. Knowing your opponent's abilities and cooldowns allows you to anticipate their next interrupt.