What is a hitbox, and why do shots miss when they look like hits?
A hitbox is the invisible shape the game uses to decide whether something was hit — and it is almost never identical to the character model you can see, which is the root of most "that should have hit" arguments.
Why models and hitboxes differ. Testing a collision against a fully detailed character mesh with tens of thousands of polygons, many times per frame, for every projectile, would be far too expensive. So games approximate with simplified shapes: capsules, spheres and boxes attached to the skeleton. These are cheap to test mathematically.
Approximation cuts both ways. A hitbox can be slightly larger than the model — so a near miss registers — or smaller, so an apparent hit does not. Loose clothing, hair, weapons and animation frames are typically excluded.
Hurtboxes and hitboxes are distinguished in fighting games: the region that deals damage versus the region that receives it, and the frame-by-frame relationship between them is the entire mechanical basis of the genre.
The bigger cause: netcode and latency. In an online game, what you see is the past. Your screen shows the server state as it was when the packet left, plus your own predicted movement.
Lag compensation addresses this by having the server rewind to reconstruct what you saw when you fired, and adjudicate the shot against that. It is why shooting where the target appears works at all.
But it creates the notorious side effects: being shot after reaching cover, because on the shooter's screen you had not yet; and "I shot first" disagreements, where both players are correct on their own timeline. These are not bugs — they are the cost of making the game feel responsive.
Hitscan versus projectile. Hitscan weapons trace an instantaneous line and register immediately. Projectile weapons simulate travel time, requiring you to lead the target — and they interact with latency differently.
Other contributors: client-side prediction correcting itself, interpolation smoothing other players' movement, peeker's advantage, animation not matching the hitbox during fast movement, and server tick rate quantising when events occur.