Porting addons to Classic

Addons for Retail will in most cases work on Classic with removal of any non-Classic API.

If you don't have an error handling addon, get BugSack or Swatter or enable CVar.

See also Patch 1.13.2/API changes.

Globe
Globe can tell you which API functions/events in an addon have been removed in Classic, if the TOC is set to the Retail version and with

For example: https://www.townlong-yak.com/globe/#h:2a8385bff94e98a6bad8f5f09b45a148-reads
 * 1) Interface:
 * 2) Globe: check-classic

API
There is a list of Classic-specific API and a complete list of Classic API. The TOC version is

You can use the WOW_PROJECT_ID global (defined in BNet.lua) to check for Classic or Retail. local isClassic = (WOW_PROJECT_ID == WOW_PROJECT_CLASSIC)

old: PlaySound("igMainMenuOptionCheckBoxOn") new: PlaySound(SOUNDKIT.IG_MAINMENU_OPTION_CHECKBOX_ON) old: PlaySoundFile("Sound/Spells/LevelUp.ogg") new: PlaySoundFile(569593)
 * Texture:SetTexture can no longer set color textures in Patch 7.0.3, use Texture:SetColorTexture(r, g, b [, a]) instead.
 * only accepts SoundKitIDs in Patch 7.0.3
 * only accepts FileDataIDs for game sounds in Patch 8.2.0

Maps
Maps were reworked in Patch 8.0.1 and the stateful API was changed to be stateless.
 * WorldMapAreaIDs were replaced with UiMapIDs.
 * It's no longer needed to call and  to get the current zone UI map, instead use ("player")

Combat Log
The combat log was reworked in Patch 2.4.0
 * The event payload is returned from since Patch 8.0.1
 * See COMBAT_LOG_EVENT for details.

Frame Scripts
Most Vanilla addons still define their frames in XML, since was only added in Patch 1.10
 * Parameters like  are no longer globals for the script handler. This was changed in Patch 4.0.1 They are now passed like so   or
 * The  parameter was unique to WoW frame scripts. It can generally be replaced with

Quick fix
There are multiple ways to handle frame scripts in XML. For simplicity's sake we will only describe a quick fix in blue text.

function SomeAddon_OnLoad(self ) self :RegisterEvent("ADDON_LOADED") end function SomeAddon_OnEvent(self, event, addon ) print(self, event, addon) end
 * Lua

   SomeAddon_OnLoad(self )   SomeAddon_OnEvent(self, event, ... )   
 * XML

Lua only
It's also possible to create a frame and handle the scripts in Lua without use of XML, depending on how simple the addon is. local function OnEvent(self, event, addon) print(self, event, addon) end local f = CreateFrame("Frame") f:RegisterEvent("ADDON_LOADED") f:SetScript("OnEvent", OnEvent)