FName

struct Core Since 1.0

#include "UObject/NameTypes.h"

Description

An immutable, case-insensitive string stored in a global name table and identified by an integer index. Comparison and hashing are O(1) regardless of string length.

Caveats & Gotchas

• Comparisons are always case-insensitive by default. 'MyActor' and 'myactor' are equal FNames. Use FString if you need case-preserving identity.
• The name table is never shrunk — every unique string created as an FName lives in memory for the entire process lifetime. Avoid creating FNames dynamically from unbounded user input.
• In Editor builds (WITH_CASE_PRESERVING_NAME), FName stores an extra display index to recover the original casing for ToString(). This makes FName larger in Editor builds than in cooked game builds.
• NAME_None (default-constructed FName) compares equal to FName(TEXT("None")). This is intentional but can surprise you when storing a tag literally called 'None'.
• FName hashing is fast but process-local and not stable across runs. Never serialize the raw integer index — always use ToString() or the FArchive operator<<.

Examples

Construction and comparison C++

FName WeaponTag(TEXT("Sword"));
FName SameTag(TEXT("sword")); // Equal to WeaponTag
ensure(WeaponTag == SameTag); // true

FString Str = WeaponTag.ToString();

Using as a TMap key C++

TMap<FName, int32> ItemCounts;
ItemCounts.Add(TEXT("Potion"), 5);
int32* Count = ItemCounts.Find(TEXT("potion")); // found — case-insensitive

Version History

Introduced in: 1.0

Version	Status	Notes
5.6	stable	—

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