GUID

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GUIDs uniquely identify almost everything the player character can interact with in World of Warcraft -- including players, pets, vehicle, and interactive world objects (think Midsummer bonfires). GUIDs are represented in WoW as a long string of hex numbers separated by hyphens.

Details

GUIDs are intended to provide a unique way to identify units; the following general rules apply:

• A monster has a single GUID from spawn until death (or despawn). When it respawns it gets a new GUID.
• Pets get a new GUID each time they are summoned.
• Monster and pet GUIDs can be recycled after server (or instance) restart.
• Players keep their GUID forever, and are unique even in cross-server battlegrounds.
• However, units that "transform" into other units may not switch GUID immediately.

GUID Types

BattlePet

• GUIDs for Battle Pets, also referred to sometimes as petID. (Not to be confused with speciesID)

BattlePet-0-[ID]

Prints the currently active companion pet.

/dump C_PetJournal.GetSummonedPetGUID()
> "BattlePet-0-00000338F951"

BNetAccount

• GUIDs for Battle.net accounts are returned from C_Club.GetMemberInfo() or C_VoiceChat.GetMemberGUID()

BNetAccount-0-[accountID]

local playerAccountGUID = string.format("BNetAccount-0-%012X", (BNGetNumFriends() + 1));
local isBattleNetGUID = C_AccountInfo.IsGUIDBattleNetAccountType(playerAccountGUID);
local isLocalPlayerGUID = C_AccountInfo.IsGUIDRelatedToLocalAccount(playerAccountGUID);
print(playerAccountGUID, isBattleNetGUID, isLocalPlayerGUID);

> "BNetAccount-0-000000000016", true, true

The accountID portion of the GUID is, at least for friend accounts, a hexadecimal form of the Battle.net account ID as used by C_BattleNet.GetAccountInfoByID()

Cast

• GUIDs for spell casts are obtained from spell cast events or as a return value from UnitCastingInfo()

Cast-[type]-[serverID]-[instanceID]-[zoneUID]-[spellID]-[castUID]

The type parameter has the following known variants.

Type	Description	Example
2	Represents a spell cast that only exists locally on the client, typically for casts that have failed due to requirements not being met.	Cast-2-0-0-0-116-000000017D
3	Represents a spell cast for an active ability, such as [Frostbolt]. Most spell casts will be of this type.	Cast-3-4170-0-8-84714-000CB03025
4	Represents a spell cast for a passive effect. These appear to be fairly rare, but may be seen on initial login.	Cast-4-4170-0-11-197886-0000302E85
13	Represents a single tick from spells such as [Divine Hymn] and [Spinning Crane Kick].	Cast-13-4170-1643-17-64844-0004B03416
16	Represents a single tick from spells such as Flurry (mage ability) and [Fists of Fury].	Cast-16-2083-0-20-228354-0000307226

For local spell casts, the server, instance, and zone ID components will always be zero, and the cast UID will be a locally-incrementing integer.

For all other known spell cast types, the cast UID component is similar to Creature and Vehicle GUIDs; the lowest 23 bits represent the timestamp of the cast measured in seconds since the UNIX epoch as returned by GetServerTime() modulo 2^23, and the higher bits appear to be an incrementing number for spell casts that occur within the same second.

ClientActor

ClientActors are NPCs which are only simulated by the game client instead of the server.

ClientActor-x-yy-zzzz

/dump UnitName("target"), UnitGUID("target")
> "Kayn Sunfury", "ClientActor-3-1-1"

Creature

• Types: "Creature", "Pet", "GameObject", "Vehicle", "Vignette"

[unitType]-0-[serverID]-[instanceID]-[zoneUID]-[ID]-[spawnUID]

/dump UnitName("target"), UnitGUID("target")
> "Hogger", "Creature-0-1465-0-2105-448-000043F59F"

local npcID = select(6, strsplit("-", UnitGUID("target")))
print(npcID)
> "448"

For Creature and Vehicle GUIDs the spawnUID component encodes a wrapping spawn time offset of the entity in the low 23 bits of the field, measured in seconds since the UNIX epoch as returned by GetServerTime() modulo 2^23. Higher bits appear to be a unique counter for individual spawns within the same time unit.

local guid = UnitGUID("target")
local unitType, _, _, _, _, _, spawnUID = strsplit("-", guid)

if unitType == "Creature" or unitType == "Vehicle" then
    local spawnEpoch = GetServerTime() - (GetServerTime() % 2^23)
    local spawnEpochOffset = bit.band(tonumber(string.sub(spawnUID, 5), 16), 0x7fffff)
    local spawnIndex = bit.rshift(bit.band(tonumber(string.sub(spawnUID, 1, 5), 16), 0xffff8), 3)
    local spawnTime = spawnEpoch + spawnEpochOffset

    if spawnTime > GetServerTime() then
        -- This only occurs if the epoch has rolled over since a unit has spawned.
        spawnTime = spawnTime - ((2^23) - 1)
    end

    print(guid)
    print("Spawned at:", date("%Y-%m-%d %H:%M:%S", spawnTime))
    print("Spawn index:", spawnIndex)
end

> "Creature-0-4170-0-41-68662-00000F4B37"
> "Spawned at:", "2021-01-25 22:50:31"
> "Spawn index:", 0

For Pet GUIDs the spawnUID component encodes a unique identifier in the low 32 bits, similar to Player GUIDs, and a wrapping counter in the upper 8 bits representing the number of times the pet has been summoned.

local guid = UnitGUID("target")
local unitType, _, _, _, _, _, spawnUID = strsplit("-", guid)

if unitType == "Pet" then
    local petUID = string.sub(spawnUID, 3)
    local spawnIndex = tonumber(string.sub(spawnUID, 1, 2), 16)

    print(guid)
    print("Unique Pet ID:", petUID)
    print("Spawn index:", spawnIndex)
end

> "Pet-0-4234-0-6610-165189-0202F859E9"
> "Unique Pet ID:", "02F859E9"
> "Spawn index:", 2

Item

• GUIDs for items are returned from C_Item.GetItemGUID, ItemMixin:GetItemGUID and GetLootSourceInfo. (Not to be confused with ItemIDs)

Item-[serverID]-0-[spawnUID]

Prints the GUID of the item in the player's head slot.

local itemLoc = ItemLocation:CreateFromEquipmentSlot(INVSLOT_HEAD)
local item = Item:CreateFromItemLocation(itemLoc)
print(item:GetItemGUID())

> "Item-1598-0-4000000A369860E1"

Player

• GUIDs for Units are returned from UnitGUID()

Player-[serverID]-[playerUID]

/dump UnitGUID("player")
> "Player-970-0002FD64"

Cross-server and GUID "uniqueness"

Player GUIDs are local on a per-server basis, making the "global" scope to be bound to the specific server. Every time a character is created, a new GUID is assigned from a simple +1 counter and then given to that character. It should be noted that the act of transferring characters, either server to server, account to account, or even account to account while remaining on the same server will generate a new character GUID, because of how the process works (the character "ceases to exist" for a short period, and is then recreated). This act erases friend and ignore lists. Renaming a character does not trigger a new GUID, as that process is much simpler than a full character move.

Uniqueness is guaranteed in cross-realm battlegrounds by masking the player GUID with a server specific unique identifier, when needed.

NPC GUID collisions have also been observed. It is unknown why or when in specific they occur, but differing mob types have had a NPC ID number which corresponded to an entirely different NPC. This is considered a very rare phenomenon.

Patch changes

• Patch 6.0.2 (2014-10-14): New format:
  • For players: Player-[server ID]-[player UID] (Example: "Player-976-0002FD64")
  • For creatures, pets, objects, and vehicles: [Unit type]-0-[server ID]-[instance ID]-[zone UID]-[ID]-[Spawn UID] (Example: "Creature-0-976-0-11-31146-000136DF91")
  • Unit Type Names: "Creature", "Pet", "GameObject", and "Vehicle"
  • For vignettes: Vignette-0-[server ID]-[instance ID]-[zone UID]-0-[spawn UID] (Example: "Vignette-0-970-1116-7-0-0017CAE465" for rare mob Sulfurious)
    
• Patch 5.1.0 (2012-11-27): Bits shifted. NPCID is now characters 6-9, not 7-10 (counting from 1).
  
• Patch 4.0.1 (2010-10-12): Bits shifted. NPCID is now characters 5-8, not 7-10 (counting from 1).
  
• Patch 3.3.0 (2009-12-08): Bits shifted. NPCID is now characters 7-10, not 6-9 (counting from 1).
  
• Patch 2.4.0 (2008-03-25): Added.
  

References

• p3lim 2014-07-20. Data Changes in WoD.
• Meorawr 2021-01-25. Creature Spawn UID Inspection.