UnitGUID

Returns the GUID of the specified unit; works on both players and NPC.

guid = UnitGUID("unit")

Arguments

unit: String - Unit ID of the unit to look up.

Returns

guid: String - a string containing the hexadecimal representation of the unit's GUID, or nil if the unit does not exist.

Example

local name = UnitName("target"); local guid = UnitGUID("target"); ChatFrame1:AddMessage(name.." has the GUID: "..guid);

Result

Cyan has the GUID: 0x00000000012729FD

Conversion to decimal?

GUIDs are 64-bit numbers, and are far too long to convert to decimal numbers using lua's libraries as a whole. E.g. running tonumber(guid, 16) will produce erronous results.

Notes

GUIDs are represented in WoW as hexadecimal strings beginning with '0x' -- this prefix is not part of the data, but merely signifies that what follows is a hexadecimal number. GUIDs are intended to provide a unique way to identify units; the following general rules apply: [1]

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.

A GUID can be thought of as being composed of multiple pieces of data. Consider "0xAABCCCDDDDEEEEEE", where:

AA: unknown.
B: unit type, mask with 0x7 to get: 0 for players, 1 for world objects, 3 for NPCs, 4 for pets, 5 for vehicles.
CCC: If the unit is a pet, CCCDDDD forms a unique ID for the pet based on creation order; if a world object, CCCDDDD is the object ID; otherwise unknown.
DDDD: If the unit is an NPC, this is the hexadecimal representation of the NPC id.
EEEEEE: If the unit is a player, this is a unique identifier based on creation order. Otherwise, this is a spawn counter based on spawn order.

Example: Determining unit type

local guid = UnitGUID("target");
local B = tonumber(guid:sub(5,5), 16);
local maskedB = B % 8; -- x % 8 has the same effect as x & 0x7 on numbers <= 0xf
local knownTypes = {[0]="player", [3]="NPC", [4]="pet", [5]="vehicle"};
print("Your target is a " .. (knownTypes[maskedB] or " unknown entity!"));

Example: Decomposing a GUID

We have a GUID: "0xF530004D2B008852".

First of all, let's find out what kind of unit it is. Take the first three digits in the GUID, ie "F53" (or 0xF53 to show it's an hex value) and apply an AND mask of 0x007 to get 0x003. This GUID is for a normal NPC, neither a pet nor a player.

We can also extract the Unit ID by taking the seventh to tenth digit and converting it to decimal form: "4D2B", or converted to decimal form "19755". A quick visit to wowhead shows that the NPC with that id is "Mo'arg Weaponsmith", [2]. All "Mo'arg Weaponsmiths" will have that id to identify them.

The last six digits, "008852" is the spawn counter. There will never be two "Mo'arg Weaponsmith", possible even never two mobs in the outside world, with the same spawn number. This spawn counter, combined with the rest makes it possible to always refer to exactly this "Mo'arg Weaponsmith", and not the one next to it.

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.

3.3 PTR changes to NPC ID portion

As of 3.3 PTR build 10522, the NPC ID has moved to CCCD instead of DDDD. For example:

 SPELL_CAST_START,0xF1308F32001790BE,"Geißelfürst Tyrannus"

The NPC portion of this is 0x8F32, which is NPC id 36658.

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