Info
All spells require the casting unit to spend a certain amount of time before the spell`s effects are applied. This time window is known as cast point or cast time. Only once the unit reaches this point does the spell take effect. The length of the cast time can vary heavily and is set for each spell individually. Usually, a specific unit`s spells share the same cast point.
An ability only applies its effects, goes on cooldown and expends mana when the casting unit successfully reaches the cast point of the spell. This means when the unit gets interrupted by disables Disables (also called crowd control, or CC) refer to any abilities or status effects that prevent, impede, or otherwise inhibit a Hero from acting. Disables come in many different varieties, and most Heroes have access or their own actions before reaching the cast point of the spell, the cast gets canceled, the spell`s effects do not get applied, it won`t go into cooldown and won`t draw mana. The player also can manually stop the spell cast by issuing a stop or halt command. When the spell cast gets interrupted during the cast time, the visual cast animation ends as well.
Instant cast
Quite a few spells have an instant cast time, meaning their effects are instantly applied as soon as the spell hotkey is pressed (if they are not targeted) or a target is chosen for the spell (if they are). Spells which require no targeting at all may not interrupt channeling spells upon cast. If a spell is targeted (be it a unit, the ground or an area) it will interrupt channeling spells, even if its cast point is instant. As for spells which require no target, there is no set rule for which of them don`t interrupt and which do, but most of the time, if a spell does not have a backswing, it does not interrupt channeling spells either.
All toggle abilities fall under this category. Toggle abilities have neither a cast point nor a backswing, and as such never interrupt a channel. This applies to most toggled items Play “Singing trio.” It has been suggested that this article or section be split into multiple new articles. Reason given: The shop should get its own page Discussion to support or oppose the split should be 
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are not considered a toggle and as such can interrupt.
Spells which are tagged as "immediate" or "toggle" (tags can be seen below) can also be cast in-between chain-disables (e.g. Sacred Arrow into Nightmare, or any disable which uses invulnerability Default buff iconPlay Error soundInvulnerability is a status effect that renders the target completely immune to all status effects and damage, except for most damage flagged as @@@#@@@HP(hp.com)###@### Removal. Most friendly effects, such as healing into a periodic area disable like Black Hole or Static Storm). These spells can also be cast after an Ancient Ancient Building Level 1 Health 4250 Health regeneration 3 Armor 15 Magic resistance 0% Collision size 298 Vision range 2600 • 2600 (G) Bounty 0 Experience 0 Notes Abilities: Backdoor Protection True Sight This article 
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Abilities with instant cast
There are 3 ways a spell can have an instant cast point:
- Its cast point is simply set to 0, in which case it will still use a cast backswing.
- It has the "DOTA_ABILITY_BEHAVIOR_IMMEDIATE" tag, which causes the spell to neither possess a cast point, nor a cast backswing.
- It has the "DOTA_ABILITY_BEHAVIOR_TOGGLE" tag, which turns the ability toggle-able, meaning it neither uses cast point nor backswing either.
If it has the "DOTA_ABILITY_BEHAVIOR_IGNORE_CHANNEL" tag, the ability simply will not interrupt channeling spells upon cast.
Unit Target
While most spells have a listed cast range, the actual range at which it can the cast will successfully go off is a bit longer than stated. This is due to movement buffer range, which is 250 range for spells. This means that if a unit moves out of cast range, but is still within 250 range more than the spell`s cast range when the spell`s cast point completes, then the spell will still be successfully cast. Only unit target spells have buffer range.
It also accepts range from unit edge to edge, based on the unit`s collision size. For example, a 150 range spell cast by a hero with a size of 24 on an enemy hero with a size of 24 can successfully go off at up to 150 + 24 + 24 + 250 = 448 range away.
Formula for maximum unit target cast range:
- Cast Range + Caster Collision Size + Target Collision Size + Buffer Range = Maximum Cast Range
Area of Effect
For area of effect spells centered on the caster, the caster`s collision size is ignored and no buffer range is added. For example, a 100 radius spell area can hit a unit with a size of 24 up to 124 range away.
Formula for maximum area range:
- Cast Range + Target Collision Size = Maximum Area Range
Point Target
For point target spells, the total cast range is simply the normal range plus the caster`s collision size. If the spell effect at the cast area has an area of effect, it follows the rules stated above.
Formula for maximum point target cast range:
- Cast Range + Caster Collision Size = Maximum Cast Range
