Specifier Reference

Specifiers accepted by UCLASS(), UPROPERTY(), UFUNCTION(), USTRUCT(), UENUM() and UINTERFACE() in UE 5.8, taken from the UC::, UP::, UF::, US::, UI:: and UM:: enumerations in Engine/Source/Runtime/CoreUObject/Public/UObject/ObjectMacros.h. Parsing is case-insensitive. Keys that only exist inside meta=(...) are listed as meta keys and never work as bare specifiers.

UPROPERTY() Specifiers

Editor Visibility and Editability

Specifier	Editable	Where it shows
`EditAnywhere`	Yes	Archetype (Blueprint defaults) and instance Details panels
`EditDefaultsOnly`	Yes	Archetype only
`EditInstanceOnly`	Yes	Placed instances only
`VisibleAnywhere`	No	Archetype and instance, read-only
`VisibleDefaultsOnly`	No	Archetype only, read-only
`VisibleInstanceOnly`	No	Instances only, read-only
`AdvancedDisplay`	—	Collapsed under the category's Advanced arrow
`SimpleDisplay`	—	Shown even when the category is in simple view
`EditFixedSize`	—	Array length cannot change in the editor
`NoClear`	—	Object reference cannot be set to null in the editor
`Interp`	—	Exposed to Sequencer tracks

A property with none of these does not appear in the Details panel.

Blueprint Access

Specifier	Read	Write
`BlueprintReadWrite`	Yes	Yes
`BlueprintReadOnly`	Yes	No
`BlueprintGetter=FuncName`	Through the named `UFUNCTION(BlueprintGetter)`	—
`BlueprintSetter=FuncName`	—	Through the named `UFUNCTION(BlueprintSetter)`
`BlueprintAssignable`	Blueprint binds events to this multicast delegate	—
`BlueprintCallable`	Blueprint can call `Broadcast` on this delegate	—
`BlueprintAuthorityOnly`	Blueprint may bind only `BlueprintAuthorityOnly` events to this delegate	—
`FieldNotify`	Property participates in MVVM field notification	—

Private members exposed to Blueprint need meta=(AllowPrivateAccess="true").

Replication

Specifier	Effect
`Replicated`	Replicated to clients; register it in `GetLifetimeReplicatedProps`
`ReplicatedUsing=FuncName`	Replicated; the named `UFUNCTION()` runs on clients when the value arrives
`NotReplicated`	Excludes a member of a replicated struct

The registration macros, COND_* conditions, push model and RPC rules are covered in ue-networking-replication.

Serialization and Config

Specifier	Effect
`Transient`	Not saved; default-initialized on load
`DuplicateTransient`	Reset when the object is duplicated
`NonPIEDuplicateTransient`	Reset on duplication except for Play In Editor
`TextExportTransient`	Skipped by text export (copy/paste, T3D)
`NonTransactional`	Changes are not recorded for undo/redo
`SaveGame`	Included by save-game archives that filter on this flag
`SkipSerialization`	Never serialized, but still reflected
`Config`	Loaded from the class's `Config=` ini section
`GlobalConfig`	Like `Config`, but only the base class section is used
`Instanced`	The referenced object is a sub-object owned by this object
`Export`	Referenced object is exported with this object
`AssetRegistrySearchable`	Value is written to the Asset Registry tags

Property Meta Keys

UPROPERTY(EditAnywhere, BlueprintReadWrite, Category="Stats",
    meta=(ClampMin="0.0", ClampMax="100.0", UIMin="0.0", UIMax="100.0",
          ToolTip="Character health, clamped to [0, 100]", DisplayName="Health Points",
          EditCondition="bHealthEnabled", EditConditionHides, AllowPrivateAccess="true"))
float Health = 100.f;

Meta key	Effect
`ClampMin` / `ClampMax`	Hard clamp on numeric input
`UIMin` / `UIMax`	Slider range without clamping typed values
`Delta`, `SliderExponent`, `LinearDeltaSensitivity`	Slider behaviour
`ArrayClamp`	Clamps an integer to the valid indices of the named array property
`ToolTip`, `ShortTooltip`	Tooltip text
`DisplayName`	Label override
`DisplayPriority`, `DisplayAfter`	Ordering inside the category
`EditCondition`	Boolean expression that enables editing
`EditConditionHides`	Hide instead of grey out when the condition is false
`InlineEditConditionToggle`	Show this bool as a checkbox next to the property that uses it
`AllowPrivateAccess`	Blueprint access to a private or protected member
`Units`, `ForceUnits`	Unit suffix (`cm`, `deg`, `s`, ...); `ForceUnits` disables conversion
`MakeStructureDefaultValue`	Default for struct members in user-defined structs
`MustImplement`	`TSubclassOf`/class pickers limited to classes implementing the interface
`MetaClass`	Base class for `FSoftClassPath` pickers
`AllowedClasses` / `DisallowedClasses`	Filter object and class pickers
`AllowAbstract`, `ExactClass`, `ShowTreeView`, `HideViewOptions`	Class picker behaviour
`RequiredAssetDataTags` / `DisallowedAssetDataTags`	Filter the asset picker by Asset Registry tags
`AssetBundles`	Bundle names for soft references in primary assets
`GetOptions`	Function returning the allowed `FName`/`FString` values
`TitleProperty`	Member shown as the array element title
`NoElementDuplicate`, `EditFixedOrder`	Array editing restrictions
`NoResetToDefault`	Hides the reset arrow
`NoEditInline`	Do not expand an `Instanced` object inline
`ShowOnlyInnerProperties`	Flatten a struct's members into the parent category
`HideInDetailPanel`	Hidden in Details, still Blueprint-visible
`HideAlphaChannel`	Colour pickers without alpha
`MultiLine`, `PasswordField`, `MaxLength`	Text field behaviour
`ContentDir`, `RelativePath`, `RelativeToGameContentDir`, `LongPackageName`, `FilePathFilter`	Path pickers
`ExposeOnSpawn`	Pin on SpawnActor / Construct Object nodes
`Bitmask`, `BitmaskEnum`	Integer edited as flags of the named `UENUM(meta=(Bitflags))`
`Categories`	Gameplay tag filter root for `FGameplayTag`/`FGameplayTagContainer` properties (read by the GameplayTags property customization, not `UM::`)
`DeprecatedProperty`, `DeprecationMessage`	Mark as deprecated with a message

UFUNCTION() Specifiers

Specifier	Effect
`BlueprintCallable`	Blueprint node with execution pins
`BlueprintPure`	Node without execution pins; implies no side effects
`BlueprintNativeEvent`	Blueprint may override; C++ body is `Name_Implementation`
`BlueprintImplementableEvent`	Blueprint implements; no C++ body
`BlueprintAuthorityOnly`	Blueprint calls run only when the owner has network authority
`BlueprintCosmetic`	Blueprint calls are skipped on dedicated servers
`BlueprintGetter` / `BlueprintSetter`	Accessor referenced by a property's `BlueprintGetter=`/`BlueprintSetter=`
`BlueprintInternalUseOnly`	Hidden from the palette (used by generated proxies)
`Server` / `Client` / `NetMulticast`	RPC executes on the server / owning client / everyone
`Reliable` / `Unreliable`	Delivery guarantee for an RPC
`WithValidation`	Requires `bool Name_Validate(...)`; returning false disconnects the caller
`Exec`	Console command on classes the console routes to (PlayerController, Pawn, HUD, GameMode, GameState, CheatManager, PlayerCameraManager, PlayerInput, GameInstance)
`CallInEditor`	Button in the Details panel
`Category="..."`	Palette grouping
`SealedEvent`	Event cannot be overridden in Blueprint
`CustomThunk`	Hand-written `execName` thunk (wildcard parameters)
`FieldNotify`	Function participates in MVVM field notification

BlueprintNativeEvent pattern:

// MyActor.h (inside the UCLASS body)
UFUNCTION(BlueprintNativeEvent, Category="Spawning")
FVector GetSpawnLocation() const;
virtual FVector GetSpawnLocation_Implementation() const;

// MyActor.cpp
FVector AMyActor::GetSpawnLocation_Implementation() const
{
    return GetActorLocation() + FVector(0.f, 0.f, 200.f);
}

Function Meta Keys

Meta key	Effect
`DisplayName`	Node title override
`ToolTip`, `ShortTooltip`	Tooltip text
`Keywords`	Extra search terms in the palette
`CompactNodeTitle`	Renders as a compact node with this title
`AdvancedDisplay`	Parameters (by name or count) hidden behind the Advanced arrow
`DefaultToSelf`	Parameter pin defaults to Self
`HidePin`	Hides a parameter pin
`WorldContext`	Parameter that receives the world context object
`CallableWithoutWorldContext`	Callable from graphs with no world context
`AutoCreateRefTerm`	Reference parameters get an inline default value
`DeterminesOutputType` / `DynamicOutputParam`	Output pin type follows a class input
`ExpandEnumAsExecs` / `ExpandBoolAsExecs`	One execution pin per enum value / per bool
`Latent`, `LatentInfo`	Latent action node with an `FLatentActionInfo` parameter
`BlueprintThreadSafe` / `NotBlueprintThreadSafe`	Allowed / disallowed in thread-safe animation graphs
`BlueprintProtected`	Only callable from the owning Blueprint class
`DevelopmentOnly`	Node compiled out of Shipping
`UnsafeDuringActorConstruction`	Not callable from construction scripts
`BlueprintAutocast`	Used as an implicit conversion node
`DeprecatedFunction`, `DeprecationMessage`	Mark as deprecated with a message

Function libraries, latent actions, async action proxies (ExposedAsyncProxy) and script bindings (ScriptMethod, ScriptName) are covered in ue-blueprint-cpp-interop.

UCLASS() Specifiers

Specifier	Effect
`Blueprintable` / `NotBlueprintable`	Allow / block Blueprint subclasses
`BlueprintType` / `NotBlueprintType`	Allow / block use as a Blueprint variable type
`Abstract`	Cannot be instantiated directly
`Config=<Name>`	`Config` properties load from `Default<Name>.ini` and the user's `<Name>.ini`
`DefaultConfig`	Saves to `Default<Name>.ini` instead of the user ini
`PerObjectConfig`	Each instance gets its own ini section, keyed by object name
`ConfigDoNotCheckDefaults`	Skip default-value comparison when saving config
`Transient` / `NonTransient`	Instances are never saved / undo a parent's `Transient`
`Deprecated`	Class is deprecated; its objects are not saved (inherited by subclasses)
`Within=<ClassName>`	Outer must be an instance of the class
`ClassGroup=<Name>`	Group in the Add Component menu (with `meta=(BlueprintSpawnableComponent)`)
`Placeable` / `NotPlaceable`	Can / cannot be placed in a level
`Const`	All properties and functions are const
`CollapseCategories` / `DontCollapseCategories`	Flatten categories in Details / undo a parent's flattening
`AutoExpandCategories=(...)` / `AutoCollapseCategories=(...)` / `DontAutoCollapseCategories=(...)`	Category expansion defaults
`HideCategories=(...)` / `ShowCategories=(...)`	Hide / re-show categories
`PrioritizeCategories=(...)`	Categories listed first
`HideFunctions=(...)` / `ShowFunctions=(...)`	Hide / re-show functions in Blueprint
`HideDropdown`	Not offered in class pickers
`MinimalAPI`	Export only type information
`CustomConstructor`	Skip the generated constructor declaration
`EditInlineNew`	Can be created inline from an `Instanced` property
`DefaultToInstanced`	Object properties of this class default to `Instanced`
`SparseClassDataType=<Struct>`	Store rarely-changing defaults in a sparse struct
`ComponentWrapperClass`	Actor exists only to wrap one component
`Experimental` / `EarlyAccessPreview`	Editor badge and warning
`EditorConfig=<Name>`	Editor-only JSON config
`Intrinsic` / `NoExport`	Class defined without generated code / header parsed for metadata only
`CustomFieldNotify`	Hand-written field-notify implementation

Class meta keys: meta=(BlueprintSpawnableComponent), meta=(ChildCanTick) / meta=(ChildCannotTick), meta=(IsBlueprintBase="true"), meta=(DisplayName="..."), meta=(ToolTip="..."), meta=(ShortTooltip="..."), meta=(IgnoreCategoryKeywordsInSubclasses), meta=(DontUseGenericSpawnObject), meta=(LoadBehavior="LazyOnDemand").

USTRUCT() Specifiers

Specifier	Effect
`BlueprintType`	Usable as a Blueprint variable, with Make/Break nodes
`Atomic`	Always serialized as a whole (no per-member deltas)
`Immutable`	Only legal in `UObject/Object.h` and being phased out; do not use on new structs
`NoExport`	No generated code; header parsed for metadata only
`BlueprintInternalUseOnly`	Hidden from Blueprint (generated helper structs)
`BlueprintInternalUseOnlyHierarchical`	As above, including all derived structs

Struct meta keys: meta=(HasNativeMake="/Script/Module.Class:Function"), meta=(HasNativeBreak="..."), meta=(HiddenByDefault), meta=(DisableSplitPin), meta=(ShowOnlyInnerProperties).

Serialization hooks and TStructOpsTypeTraits (WithSerializer, WithNetSerializer, WithIdenticalViaEquality, ...) are covered in ue-serialization-savegames and ue-networking-replication.

UENUM() Specifiers

Specifier / meta	Effect
`BlueprintType`	Usable in Blueprint (requires `enum class : uint8`)
`meta=(Bitflags)`	Values are bit flags; pair with `UPROPERTY(meta=(Bitmask, BitmaskEnum="/Script/MyGame.EMyFlags"))`
`meta=(UseEnumValuesAsMaskValuesInEditor="true")`	Enumerators already hold mask values instead of bit indices
`meta=(ScriptName="...")`	Name exposed to scripting

UMETA per-value keys:

Key	Effect
`DisplayName="Label"`	Name shown in Blueprint and the editor
`Hidden`	Removed from pickers (sentinels such as `MAX`)
`ToolTip="text"`	Tooltip for the value

UENUM(BlueprintType)
enum class EMyGamePhase : uint8
{
    PreGame    UMETA(DisplayName="Pre-Game"),
    InGame     UMETA(DisplayName="In Game"),
    PostGame   UMETA(DisplayName="Post-Game"),
    MAX        UMETA(Hidden)
};

Replicated enum properties must fit in a byte: declare enum class : uint8. TEnumAsByte<T> exists only for legacy namespaced enums (namespace EMyOld { enum Type { ... }; }).

UINTERFACE() Specifiers

Specifier	Effect
`Blueprintable` / `NotBlueprintable`	Blueprint classes may / may not implement the interface
`MinimalAPI`	Export only the type information of the `U` stub
`ConversionRoot`	Root of a Blueprint conversion hierarchy
`meta=(CannotImplementInterfaceInBlueprint)`	C++-only interface; functions may then be plain virtuals or `BlueprintCallable` without `BlueprintNativeEvent`

Native-only interface (no Blueprint implementation):

// MyDamageable.h
#pragma once
#include "CoreMinimal.h"
#include "UObject/Interface.h"
#include "MyDamageable.generated.h"

UINTERFACE(MinimalAPI, NotBlueprintable, meta=(CannotImplementInterfaceInBlueprint))
class UMyDamageable : public UInterface
{
    GENERATED_BODY()
};

class MYGAME_API IMyDamageable
{
    GENERATED_BODY()
public:
    virtual void ApplyMyDamage(float Amount, AActor* DamageInstigator) = 0;
};

// MyTarget.h
#pragma once
#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "MyDamageable.h"
#include "MyTarget.generated.h"

UCLASS()
class MYGAME_API AMyTarget : public AActor, public IMyDamageable
{
    GENERATED_BODY()
public:
    virtual void ApplyMyDamage(float Amount, AActor* DamageInstigator) override;
};

// Calling a native interface
void DamageIfPossible(AActor* Target, float Amount, AActor* Source)
{
    if (IMyDamageable* Damageable = Cast<IMyDamageable>(Target))
    {
        Damageable->ApplyMyDamage(Amount, Source);
    }
    bool bImplements = IsValid(Target) && Target->Implements<UMyDamageable>();   // type check without casting
}

Interfaces that Blueprint may implement use BlueprintNativeEvent/BlueprintImplementableEvent functions and are invoked through the generated Execute_FunctionName statics; that pattern, plus TScriptInterface<T> properties, is covered in ue-blueprint-cpp-interop.

/ue-cpp-foundations

referencesproperty-specifiers.md