How addons change a WoW UI

Ever wondered what an addon actually does to your game? An addon changes your World of Warcraft screen. It does not change the dungeon, your gear, or what other players see. The Warcraft Wiki describes an addon as Lua and XML that augments, modifies, or replaces the default user interface. It can show something Blizzard’s UI never drew, add a button, move and recolor what is already there, or throw the default UI out and draw its own.

I play Devastation Evoker as Tingyoudied on EU-Ravencrest. 2849 in Blitz, mostly RBGs. Trinket and interrupt sit on the scroll wheel. The spec write-up is the Evoker PvP guide. This isn’t a 20-folder shopping list. It’s a look at what those folders actually do to your screen. The short install list lives on Best WoW addons. The PvP cut is Best WoW PvP addons. More under Guides.

What the default UI already is

Before any addon, the screen is Blizzard’s. Unit frames, action bars, the chat window, nameplates, and bags are frames the game created. Since Dragonflight, Edit Mode lets you move a lot of those frames yourself. Blizzard’s own HUD post says you open it from the Game Menu with Escape, then name and save a layout. An addon is not required to slide your bars ten pixels left.

That same post is plain about addons. Edit Mode does not replace them. The base UI grew pieces some addons used to own, so a player who never opens CurseForge can still move a frame. An addon earns its place when Edit Mode cannot answer the question. The pull is happening and you still cannot see the mechanic, the enemy cast, or whether your own cast went out. Best WoW addons keeps that test. If you cannot say what question the addon answers, it is decoration.

Pick the gap first. The line under the menu is the smallest change that covers it.

Pick the thing the default screen is failing to show you.

What is going wrong?A mechanic hits me with no warningI cannot read an enemy castI cannot tell if my casts are going outI need one reminder the default UI hidesI want the whole screen rearranged

Add one boss-mod family, Deadly Boss Mods or BigWigs, and learn its sounds. A second one talking over the first does not make the mechanic clearer.

Three ways an addon touches the screen

It draws something new. A boss-mod family puts a timer on a mechanic the default screen only shows once the cast has started, or not at all. Deadly Boss Mods or BigWigs is that job. Pick one family. Two of them talking at once is worse than one. A damage meter lists casts that already happened. A single WeakAuras bar can sit next to your buttons for one cooldown you keep forgetting. None of these replace the health bar. They add a frame beside it.

It restyles a frame you already have. Unit-frame addons change how health, resource, buffs, and debuffs are drawn. Nameplate addons make an enemy cast large enough to read. What a nameplate is is the frame. Plater is the usual named product when the default options are not enough. Bar addons regroup your buttons. The spell and the enemy stay the same. You have only changed the drawing.

It replaces the default UI. ElvUI is the usual example. It draws its own version of the screen, and the install shows up as a few entries you enable together, including its options. If you then install a separate chat, bar, or nameplate addon, you get two copies of that piece unless you turn ElvUI’s module for it off. A replacement does not stack politely on top of another addon that wants the same frames. ElvUI is not my logged UI. The Evoker guide says the screen is built around clear action bars and seeing enemy cooldowns. That is a job list, not a brand list.

What Midnight still lets an addon do

Midnight is the live expansion, and Blizzard changed the rule for combat addons before it shipped. The posts are plain about the split. Addons should not automate combat decisions. They should still be able to change how information is presented.

How Midnight’s Upcoming Game Changes Will Impact Combat Addons is the customization post. In Blizzard’s own examples, an addon can still change raid frames, nameplates, action bars, panels, fonts, and art. The new boss-warning timeline can be shown another way, including as a stack of countdown bars, and an author can add a custom event such as a break timer. The brighter “important cast” state on a nameplate can be made larger or given a different animation. If the default UI is already showing a combat fact, an addon can usually present that fact differently.

What it is not supposed to do is read that fact and decide which button you press. A timer that repeats a warning the game is already showing is a different thing from an addon that watches the fight and calls the next spell.

Combat Philosophy and Addon Disarmament in Midnight is the engineering post. Combat state is a “secret value.” Addons can display it. They cannot “know” it. Blizzard’s picture is a black box. An addon can change the size, the shape, and the color of the box. It cannot look inside and tell you whether a specific debuff is up, or what a cooldown still has left, with the certainty older combat addons used for logic. The same post says the goal was a level playing field, not a prettier screenshot.

Blizzard also said the goal was to leave non-combat information alone. Bags, maps, and the rest of the out-of-combat screen were not the target. Damage meters and boss mods were, because they had been reading the fight as it happened. The base UI grew its own boss warnings so that information would not live only inside an addon. Midnight already draws personal cooldowns, allied defensives, and diminishing returns in the base UI. That is why the PvP addon page tells you not to stack a second DR tracker on the native one.

I burst stacked groups in Blitz. Spatial Paradox plus Font of Magic is a range-and-Fire-Breath plan. The plate has to show the cast I am kicking. The addon may restyle that plate. It is not supposed to pick the kick for me. The scroll wheel is still the bind.

Details! from the project page

Details! Damage Meter is the meter I will name, and I will name it from Terciob’s CurseForge project page, not from a Discord. The page’s own line is complete combat analysis, gathering damage, healing, and other combat data. The same page says Details! updates in real time, and that you should not trust a source that says it only updates after combat.

That is a drawing job. After a Blitz I use it to see whether a Fire Breath or a Deep Breath actually went out. I do not put the meter on the node. In a stacked flag fight I am looking at plates and the scroll wheel, not a pie. Two meters are two parsers and one extra crash surface. Pick one.

Official policy, since patch 3.1

The wiki records the rule that arrived with patch 3.1. Addons must be available free of charge. They may not include advertisements or solicit donations in-game. Blizzard’s UI Add-On Development Policy is the longer list. Code must be visible, not obfuscated. The addon must not harm realms or other players. It must stay inside the game’s rating. A paid “pro UI pack” from a random site is not how this works, and it is a common way to hand an account over.

Download from CurseForge, Wago, or that addon’s own project page. The addon manager is how the folder gets there. One app, one Retail folder. A zip that asks you to run an .exe is not an addon. An addon is just a folder of Lua and XML files with a .toc file. If a ‘pack’ asks you to run an .exe, don’t.

Where the change actually loads

An addon is files in a folder, not a setting buried in the graphics menu. For the retail client, that folder is _retail_, then Interface, then AddOns. Classic, Mists, and the other clients have their own folders beside _retail_. Installing into the wrong one is why an addon “does nothing.”

The Warcraft Wiki’s install path is World of Warcraft\Interface\AddOns\AddonName\AddonName.toc. The folder name and the .toc name have to match. The .toc is the manifest. It lists the Lua and XML the client should load, and it prints an Interface number for the patch the author targeted. For 12.1.5 that number is 120105 on the wiki’s TOC page. If the number does not match this client, the addon is marked out of date.

The reliable way to find the folder is the Battle.net page for World of Warcraft, then the option that reveals the install on disk. That opens the copy you launch, which matters if an old install is still on the disk. Wowhead’s install guide says the same thing another way. Right-click the shortcut you actually use and open the file location, then _retail_, then Interface, then AddOns. Put the addon’s own folder inside AddOns, so the addon’s .toc file sits one level down, not buried in an extra folder that came out of the zip. Restart the game. On the character select screen, the AddOns button lists what it found. Check the ones you want.

After a patch, the client marks addons that have not been updated for that version as out of date and will not load them unless you check “Load out of date AddOns” on that same list. The wiki is explicit. Blizzard clears the checkbox on each patch, so it comes back unchecked. An out-of-date addon sometimes still works. Sometimes it throws errors across the screen. Update the ones you need, and leave the checkbox off for anything you are not willing to test.

A /reload reloads files the client already knew about. A brand-new folder, or a new file the author added in an update, is why a full restart still matters. Wowhead’s addon-coding guide is the competitor page that keeps repeating that split, and it matches what the wiki says about detecting a new .toc.

When two addons fight

Addons load on top of Blizzard’s frames, and on top of each other. Two nameplate addons both try to own the plates. A full UI replacement and a bar addon both try to own the bars. The result is overlapping frames, or a frame that jumps back to where the other addon put it. Gladius and sArena both exist as arena frames. OmniBar and BigDebuffs both exist as cooldown and aura highlighters. They are products. They are not my logged UI. If you install two of them plus a WeakAura pack plus the native cooldown display, one event becomes two icons.

Turn off everything, then enable one addon and confirm the screen did the thing you asked. If the UI errors, the last one you enabled is the first one to remove. The wiki’s troubleshooting note, in place since patch 2.3, is the message that an interface action failed because of an addon. That means one of them blocked something Blizzard’s UI was trying to do. The wiki’s next step is /console taintLog 1, reproduce, then read Logs\taint.log for the word blocked. In practice, the rule is simple. Disable extras, then add one folder back.

A dependency is the other failure. Some addons will not load unless another folder is enabled. The addon list says so. Enable the missing one, or remove the plugin that needed it. Do not stack a second copy of Details because the first one looked empty.

Settings, crashes, and what the folder remembers

An addon can save settings. Wowhead’s install and coding pages put those files under WTF\Account, either account-wide or per character, named after the addon. They write when you reload, relog, or close the game cleanly. A crash can drop a session of meter data because the write never happened. That is why a Details window can look empty after a hard close. It is not a second product. It is the save the client did not finish.

That is also why two managers on one folder are a bad idea. One app updates Details. The other rolls it back. You get two copies, or a half-written .toc. Pick CurseForge, Wago App, or WowUp. Not two of them on Retail.

What an addon cannot change

Other players do not see your nameplates, your timer, or your bars. An addon cannot grant a spell or change a boss. It also cannot survive a patch by itself. Best WoW addons covers the order for a patch day. Update boss mods and nameplates first, try a city and a trivial fight, and remove the last addon you updated if the UI errors. An addon is a layer on Blizzard’s UI. When that UI changes, the layer has to be updated, or turned off.

It cannot raise a 2849. Binds still beat folders. Scroll-wheel trinket and interrupt will outlive any WeakAura pack I import. If the default plate already shows the cast, Plater is paint. If Edit Mode already moved the bar, ElvUI is a second screen you have to maintain. If you cannot name the job, turn the folder off.

Add one addon for the one fact the default screen still hides. Stop there. More under Guides.

Common questions

What is a WoW addon?

A small program that changes World of Warcraft's interface. Addons can add new information, restyle frames like nameplates and raid frames, or replace parts of the default UI.

Can addons still change the UI in Midnight?

Yes. Addons can still restyle raid frames, nameplates, action bars, and fonts, though Blizzard has limited what combat information they can calculate.

Where do WoW addons go?

In the Interface\AddOns folder inside your game's _retail_ folder. Then enable them from the AddOns button on the character select screen.

Are WoW addons allowed?

Yes. Blizzard allows addons as long as they're free and only change the interface. They can't play the game for you.