Glossary¶

Alphabetical definitions of GAS-specific terms. For acronym expansions, see Acronyms.

Ability System Component (ASC): UAbilitySystemComponent — the UActorComponent that serves as the central hub for GAS. Owns granted abilities, active effects, attribute sets, and tag state. See ASC.
Ability Task: UAbilityTask — a latent action that runs within the scope of an active UGameplayAbility. Ends when the ability ends. Blueprint-exposable via output delegates. See Ability Tasks.
Active Gameplay Effect: FActiveGameplayEffect — the runtime wrapper for a UGameplayEffect that has been applied to an ASC. Tracks remaining duration, stacks, and inhibition state.
Active Gameplay Effect Handle: FActiveGameplayEffectHandle — a lightweight handle (int32) used to reference an active effect without holding a pointer. Safe to store; becomes invalid when the effect is removed.
Aggregator: FAggregator — internal engine struct that collects all modifiers targeting a single attribute and evaluates them via the modifier formula. One aggregator exists per attribute per ASC.
Async Ability Task: UAbilityAsync — a latent task similar to UAbilityTask but usable outside of abilities (e.g., in UMG widgets, AI). Does not require an active ability. See Async Ability Tasks.
Attribute: A single numeric property (float) within a UAttributeSet, wrapped in FGameplayAttributeData. Attributes are the only values that Gameplay Effects can modify.
Attribute Set: UAttributeSet — a UObject that defines a group of related attributes. Registered with an ASC. See Attributes and Attribute Sets.
CDO (Class Default Object): The singleton template instance of a UClass. GAS uses CDOs for abilities with InstancedPerExecution or NonInstanced instancing policies — the CDO is shared across all activations.
Cooldown Effect: A UGameplayEffect with HasDuration used as an ability's cooldown. The ability checks for the cooldown tag before activation. See Cooldowns and Costs.
Cost Effect: A UGameplayEffect (typically Instant) applied when an ability commits. Deducts resource attributes (mana, stamina, etc.).
Dynamic Gameplay Effect: A UGameplayEffect created at runtime via NewObject<UGameplayEffect>() rather than a data asset. Useful for procedural modifiers. See Dynamic Effects.
Evaluation Channel: EGameplayModEvaluationChannel — an optional channel that allows modifiers to be evaluated in separate passes. The output of one channel feeds as the base value into the next. Disabled by default; enabled via Developer Settings.
Execution Calculation (ExecCalc): UGameplayEffectExecutionCalculation — a C++ class that can read multiple attributes and output multiple modifier results in a single pass. Used for complex operations like damage formulas. See Execution Calculations.
FGameplayAbilitySpec: The runtime record of a granted ability. Contains the ability CDO/instance, level, input ID, activation state, and the granting GE handle (if any).
FGameplayAbilitySpecHandle: A lightweight handle used to reference a granted ability without holding a pointer.
FGameplayAttributeData: The struct wrapping a single attribute value. Contains BaseValue (before modifiers) and CurrentValue (after modifiers are evaluated).
FGameplayEffectContext: Runtime context passed with a GE application — instigator, causer, hit result, etc. Can be subclassed via UAbilitySystemGlobals::AllocGameplayEffectContext().
FGameplayEffectSpec: The runtime instance created when a UGameplayEffect is about to be applied. Contains the GE definition plus captured context: level, source/target tags, SetByCaller magnitudes, and modifier snapshots.
FGameplayTag: A single hierarchical tag registered in the engine's tag system (e.g., Status.Debuff.Stun). Lightweight (stored as FName internally). See Gameplay Tags.
FGameplayTagContainer: An unordered set of FGameplayTag values. Used throughout GAS for tag queries, requirements, and grants.
FPredictionKey: A key generated on the client to associate predicted actions (ability activations, GE applications) with their server-confirmed counterparts. See Prediction.
Gameplay Cue: A cosmetic-only notification (VFX, SFX, camera shake) triggered by tags matching GameplayCue.*. Never affects gameplay state. See Gameplay Cues.
Gameplay Effect: UGameplayEffect — a data-only blueprint that defines attribute modifiers, tag grants, duration, stacking, and more. The primary data pipeline of GAS. See Gameplay Effects.
Gameplay Effect Component (GEC): UGameplayEffectComponent — a modular behavior object that lives within a UGameplayEffect (UE 5.3+). Replaces the monolithic tag/ability/immunity fields with composable components. See GE Components.
Granted Tag: A Gameplay Tag added to the target's owned tag set while a duration or infinite GE is active. Removed when the GE expires or is removed.
I-frames (Invulnerability Frames): A brief window during an action (like a dodge roll) where the character cannot take damage. Typically implemented by granting State.Invulnerable via Activation Owned Tags, then checking for that tag in the damage pipeline. See Dodge Roll Recipe.
Inhibited Effect: An active GE whose ongoing tag requirements are not met. It remains applied but dormant -- its modifiers and granted tags are not active. Becomes active again when requirements are satisfied.
Meta Attribute: An attribute used as a transient calculation channel (e.g., IncomingDamage) that is never replicated or persisted. Consumed immediately in PostGameplayEffectExecute and reset to zero. See Damage Pipeline.
Modifier: A single attribute modification within a GE — defined by an attribute, operation (EGameplayModOp), and magnitude. See Modifiers.
Modifier Magnitude Calculation (MMC): UGameplayModifierMagnitudeCalculation — a C++ class that computes a single modifier's magnitude by reading attribute values and tags at runtime. See Magnitude Calculations.
Net Execution Policy: EGameplayAbilityNetExecutionPolicy — controls where an ability's logic runs: LocalPredicted, LocalOnly, ServerInitiated, or ServerOnly. See Net Execution Policies.
Prediction Key: See FPredictionKey.
Prediction Window: A scope during which the client predicts the outcome of an action before the server confirms or rejects it. Created with FScopedPredictionWindow. See Prediction.
Net Relevancy: Whether an actor is close enough to a player to be replicated. Actors outside a player's net cull distance are not replicated, which affects ASC state visibility for distant actors.
Replication Mode: EGameplayEffectReplicationMode — controls what GE data is replicated to which clients: Full, Mixed, or Minimal. See Replication Modes.
Scalable Float: FScalableFloat — a float value optionally multiplied by a curve table row evaluated at a given level. Used for magnitudes, durations, periods, and cooldowns. See Scalable Floats.
SetByCaller: A magnitude type where the value is set on the FGameplayEffectSpec at runtime using a Gameplay Tag as a key. See SetByCaller.
Spec Handle: See FGameplayAbilitySpecHandle or FActiveGameplayEffectHandle depending on context.
Stacking: The rules governing what happens when multiple instances of the same GE definition are applied: AggregateBySource, AggregateByTarget, or no stacking. See Stacking.
Target Data: FGameplayAbilityTargetData — polymorphic struct carrying targeting results (hit results, actor lists, locations). Replicated from client to server for confirmed targeting. See Target Data.