Hitbox (Collision Area)

What exactly is a hitbox?

Picture an invisible outline around the hero. When an attack or ability touches or enters that area:

The hero takes damage or suffers an effect (such as a stun, root, etc.).
The attack hits, even if the ability's visual seems to just "graze" the target.

If you cast a skillshot ability (e.g. Sylvanas's Wailing Arrow or Stitches's Hook), it only hits the enemy if it enters their hitbox.
Heroes like Murky have a very small hitbox, making them harder to hit.
On the other hand, heroes like Cho'gall or Deathwing have huge hitboxes, so they are much easier to hit with area spells and precision attacks.

Hitbox size affects your survivability, movement, and likelihood of being hit.
Heroes with a small hitbox have an edge when dodging.
Heroes with a large hitbox can block paths or shield allies ("body block").

Hero	Approximate Radius	Category
Ana	0.5625	Very Small
Valla	0.6250	Very Small
Nova	0.6250	Very Small
C.t.e	0.6250	Very Small
Orfèa	0.6250	Very Small
Deckard	0.6250	Very Small
Tracer	0.6250	Very Small
Jaina	0.6250	Very Small
Sylvana	0.6250	Very Small
Illidan	0.6250	Very Small
Tyrande	0.6250	Very Small
Qhira	0.6250	Very Small
Valira	0.6250	Very Small
Anduin	0.6250	Very Small
Li Li	0.6250	Very Small
Alexstrasza	0.6250	Very Small
Crona	0.6250	Very Small
Auriel	0.6250	Very Small
Li-Ming	0.6250	Very Small
Murquinho	0.6250	Very Small
Kharazim	0.6250	Very Small
Maltael	0.6875	Small
Kerrigan	0.6875	Small
Sondius	0.6875	Small
Lucio	0.6875	Small
Junkrat	0.6875	Small
Hanzo	0.6875	Small
Greymane	0.6875	Small
Nazibo	0.6875	Small
Genji	0.6875	Small
Samuro	0.6875	Small
Gall	0.6875	Small
Stukov	0.6875	Small
Xul	0.6875	Small
Cássia	0.6875	Small
Sonya	0.7500	Small
Varian	0.7500	Small
Mefisto	0.7500	Small
Medivh	0.7500	Small
Rehgar	0.7500	Small
Yrel	0.7500	Small
Lunara	0.7500	Small
Uther	0.7500	Small
Zul'jin	0.7500	Small
Tyrael	0.7500	Small
Thrall	0.7500	Small
Zeratul	0.7500	Small
Malfurion	0.7500	Small
Johanna	0.7500	Small
Gazlowe	0.7500	Small
Ten.morales	0.7500	Small
Abathur	0.7500	Small
Maiev	0.7500	Small
Tassadar	0.8125	Medium
Tychus	0.8125	Medium
Gul'dan	0.8125	Medium
Raynor	0.8125	Medium
Arthas	0.8125	Medium
Artanis	0.8125	Medium
Imperius	0.8125	Medium
Falstad	0.8125	Medium
Kael'thas	0.8125	Medium
Zarya	0.8125	Medium
Leoric	0.8125	Medium
Muradin	0.8125	Medium
Alarak	0.8125	Medium
Mal’ganis	0.8750	Medium
Rexxar	0.8750	Medium
Hogger	0.8750	Medium
Garrosh	0.8750	Medium
Mei	0.8750	Medium
Kel'thuzad	0.8750	Medium
E.T.C.	0.9375	Medium
Açougueiro	0.9375	Medium
Blaze	0.9375	Medium
Chen	0.9375	Medium
Ragnaros	1.0000	Medium
Dehaka	1.0000	Medium
Anubarak	1.0625	Large
Zagara	1.1250	Large
Fenix	1.1250	Large
Suturino	1.1250	Large
Azmodan	1.1875	Very Large
Cho	1.1875	Very Large
D.va	1.1875	Very Large
Diablo	1.1875	Very Large
Sgt.marreta	1.1875	Very Large
Deathwing	1.2500	Very Large