Vision is a gameplay mechanic which determines what a unit can and cannot see. Areas a unit cannot see are filled with the Fog of War, the dark places of the map where no ally currently has vision of. Unit vision is written in a Day / Night format. If a unit has 1800 vision range during the day and 800 vision range at night, it will be written as 1800 / 800.
Fog of War
To reveal units in the fog of war, an allied unit or ability must gain vision in that area. Observer Wards can provide vision in a large area to their team. The Roshan pit has a deep fog that cannot be seen into unless there is an ally inside it or a unit has flying vision.
If a unit in the fog of war attacks an enemy that does not have vision of them, the attacker will be revealed for a few seconds.
Day and Night cycle
Most units have different vision ranges for the day and night cycle. Generally, units see a lot farther during the day than they do at night. Most heroes have 1800 vision range during the day, and 800 at night, though there are several exceptions. This makes ganking more viable at night, because heroes can get much closer without being detected.
Below is a table of all exceptions to the 1800 / 800 hero vision rule:
|Hero||Day Vision||Night Vision||Notes|
|Luna||1800||1800*||Luna obtains 1800 night vision permanently after leveling Lunar Blessing|
|Lycan||1800||1800*||Lycan obtains 1800 night vision while Shapeshift is active|
|Slardar||1800||1800*||With level 20 talent|
|Spirit Breaker||1800||1400*||With level 10 talent|
|Winter Wyvern||1800||1200(1700)*||Winter Wyvern obtains 1200 night vision while Arctic Burn is active and an permanent 500 extra night vision with level 15 talent|
This is the default for most units. They cannot see areas that are on higher ground than themselves, and units on higher ground receive unobstructed vision below. Trees will also block vision, and can be used to escape enemies by running through small gaps in between them. Trees can be cut down or destroyed to no longer block vision.
Sources of ground vision from spells:
|Hero||Ability||Ground Vision Radius||Vision Duration|
|Ancient Apparition||Ice Vortex||200||16|
|Crystal Maiden||Crystal Nova||900||6|
|Disruptor||Kinetic Field||325||2.5 / 3 / 3.5 / 4|
|Elder Titan||Astral Spirit||400||8|
|Techies||Proximity Mines||64||Until detonated|
|Remote Mines||700||10 minutes|
|Item||Ability||Ground Vision Radius||Duration|
|Observer Ward||Plant Ward||1600||7 minutes|
|Sentry Ward||Plant Ward||150||12|
|Manta Style||Mirror Image||1000||0.23|
This provides unobstructed vision at all levels of elevation. A unit with flying vision can see the high ground above them, and will not have their vision blocked by trees.
Sources of flying vision from spells:
|Hero||Ability||Flying Vision Radius||Vision Duration|
|Alchemist||Unstable Concoction Throw||300||Projectile duration|
|Ancient Apparition||Ice Blast||500||3|
|Firefly||Current vision range||18|
|Beastmaster||Wild Axes||350||Projectile duration|
|Faceless Void||Chronosphere||475||4 / 4.5 / 5 |
4 / 5 / 6 with Aghanim's Scepter
|Keeper of the Light||Illuminate||375||10.34|
|Lich||Chain Frost||800||Projectile duration|
|Medusa||Mystic Snake||100||Projectile duration|
|Mirana||Sacred Arrow||500||Projectile duration, then 3|
|Monkey King||Tree Dance||800||While perched|
|Nature's Prophet||Sprout||500||3 / 3.75 / 4.5 / 5.25|
|Phantom Assassin||Stifling Dagger||450||Projectile duration, then 3.34|
|Shadow Demon||Shadow Poison||190||Projectile duration|
|Skywrath Mage||Arcane Bolt||325||Projectile duration, then 3.34|
|Concussive Shot||300||Projectile duration, then 3.34|
|Storm Spirit||Static Remnant||500||12|
|Ball Lightning||400||While in use|
|Treant Protector||Eyes In The Forest||700||Tree duration|
|Tusk||Ice Shards||150||Projectile duration|
|Vengeful Spirit||Wave of Terror||500||3|
|Venomancer||Venomous Gale||400||Projectile duration|
|Item||Ability||Flying Vision Radius||Duration|
|Shiva's Guard||Arctic Blast||800||4.5|
Shared vision provides an area of vision over an enemy unit equal to that enemy unit's vision range.
Sources of shared vision:
|Spirit Breaker||Charge of Darkness|