Build-UpGive feedback
Build-up is a mechanic that causes bullets to accumulate a status effect over multiple hits.
Whenever a hero fires at an enemy, items and abilities with Build-up add a percentage to a meter on that target. Once the meter reaches 100%, the associated status effect is triggered. The progress of a build-up is shown as round icons above the target. Build-up per shot is reduced by damage falloff, dropping to as low as 10% of its base value at maximum range.
Build-up is a related but distinct mechanic from Stacks. Unlike stacks, which are discrete increments that scale an ongoing effect, build-up functions as a percentage meter that triggers a single status effect upon reaching 100%.
Items
Items with Build-up apply their percentage to the target through bullet hits. The build-up meter decays if the enemy does not receive any new stacks for 2 seconds, at a rate of 20% per second. Melee attacks count as 1 shot for build-up purposes. Each item's build-up per shot varies by hero, as it is affected by the hero's weapon fire rate and clip size; the exact percentages can be found on each item's page.
| Name | Effect on Trigger |
|---|---|
 Slowing Bullets |
Movement Slow |
 Weighted Shots |
Movement Slow |
 Silencer |
Silence |
 Inhibitor |
Damage Reduction and Healing Reduction |
 Toxic Bullets |
Bleed |
 Spiritual Overflow* |
Spirit Overflow |
* Spiritual Overflow is a special case: its build-up affects the shooter rather than the target. However, the build-up meter still accumulates on the target being shot, meaning it is impossible to accelerate the process by shooting multiple different targets at once. It is also the only build-up source where the progress is not shown above the target.
Heroes
Some heroes have abilities that use the Build-up mechanic, accumulating a percentage on the target until the associated effect triggers.
Infernus — 
Afterburn: triggers a Burn (damage over time) effect. Light Melee attacks count as 1 stack; Heavy Melee attacks count as 2 stacks.
Mina — 
Love Bites: triggers a Spirit damage proc. Melee attacks do not contribute to build-up.
Mirage — 
Djinn's Mark: builds up stacks by shooting the target at certain intervals, triggering either when the timer runs out, when max stacks are reached, or when detonated by Mirage. Builds up with any amount of bullet damage.
Silver — 
Slam Fire (Tier 3): deals bonus damage if all 3 shots hit the same target.
Note: 
Graves' 
Essence Theft appears visually as a Build-Up, but it's actually a stacking effect, as the effect is applied over time.
Counters
Several items can mitigate or counter build-up effects:
- Items providing debuff resist reduce the lingering duration of build-up as well as making already thiggered effect disappear quicker.
Debuff Reducer and its upgrades 
Spellbreaker and 
Unstoppable
Blood Tribute- Weighted Shots
Plated Armor provides a chance to block bullet effects from incoming shots entirely, which includes any build-up effects.
Juggernaut slows fire rate of nearby attackers, making it harder for enemies to stack build-up quickly.
It is worth noting that 
Metal Skin, despite providing immunity to bullet damage, does not protect against build-up in any way; shots negated by Metal Skin still contribute their full build-up percentage.
