Addon

Synonyms:	Addon, Add-on
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General

An AddOn (or Addon, Add-on) for the MMORPG World of Warcraft is a third-party software, usually created by fans and gamers. AddOns are technically Mods. Some can work as stand-alone programs, but most require WoW to run in order to work. AddOns enhance or alter parts of the game UI, from minor tools showing additional information up to programs that change the entire interface of the game or add additional functionality. They have grown to be indispensable tools for a lot of players.

Legal Situation

In their Terms of Use WoW-developer Blizzard Entertainment forbids the use of modifying third-party software in order to prevent players from gaining unfair advantages. For example, any form of automated playing through bots is prohibited. Violation of the ToU results in account banning and has also caused at least one lawsuit against a developer. However, exceptions are made for AddOns that follow the World of Warcraft User Interface Add-On Development Policy. This has led to the creation of many AddOns that enhance game functions and interface components, some of which have been "integrated" by Blizzard in later patches (i.e. they took the idea and created a similar tool as part of the official game).

World of Warcraft User Interface Add-On Development Policy

In 2004 Blizzard Entertainment introduced the World of Warcraft Bug Exploitation and Client/Server Manipulation Policy as part of their game policies. It covered topics such as bug exploitation, abuse of game mechanics, data mining and also third-party software. Blizzard Entertainment prohibited any form of third-party software used to gain advantage, but excluded UI modifications from the ban, actively encouraging gamers to develop user interface enhancing addons:

We definitely want people to create their own UIs utilizing custom menu configurations, graphics, and even sounds. Anything that can be coded to modify the style and the look of the UI is fair game, as long as the modifications are done to the sanctioned internal files of the game.

2009 the World of Warcraft User Interface Add-On Development Policy was released. It featured an eight-point guideline for AddOn developers:

1. Add-ons must be free of charge.
2. Add-on code must be completely visible.
3. Add-ons must not negatively impact World of Warcraft realms or other players.
4. Add-ons may not include advertisements.
5. Add-ons may not solicit donations.
6. Add-ons must not contain offensive or objectionable material.
7. Add-ons must abide by World of Warcraft ToU and EULA.
8. Blizzard Entertainment has the right to disable add-on functionality as it sees fit.

Point four and five caused some uproar in the community, as especially developers of more complex AddOns relied on in-game adverts for donations to continue their work (usually a small button or link on the AddOn options interface).

Script Language

WoW AddOns are written in Lua. Due to the availability of online tutorials as well as WoW-related programming literature quite a few gamers give it a try and start practicing on small AddOn codes. Additionally, the XML engine provides the frame to create and customize user interfaces.

Examples

WoW AddOns fall into various categories, including, but not limited to: class specific tools, chat and communication, quests, professions, combat, unit frames, auction and economy, buffs and debuffs, inventory and more. They may be very small, for example to add a single line of information to a tooltip, or quite large and powerful, such as unit frames or raid analysis programs.

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  LootDB just adds a few lines of information at the bottom of the tooltip.

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  Auctioneer on the other hand not only changes the layout of the auction house window, it also adds extensive tools to organize, search, buy or sell.

Community

AddOns and their scripting are an important part of the Wow Community as many players rely on them. Especially in competitive areas of WoW, such as raiding or PvP, it's almost unthinkable to play without some core AddOns. Other gamers prefer to have the option of highly customizable interface designs, others are looking for tools to simplify certain actions and so on. There are countless topics on what AddOn is better suited for this or that task, play styles are compared, functionality is discussed and on every major patch day players are busy with updating their AddOns, sometimes seeing the original UI for the first time again in ages.

Interestingly, when Blizzard first started to implement fan-made Addons into the game's UI, there were players opposing this idea, stating that these things would "dumb down" the game experience.

Patch 1.3 also implemented the ability to display quest objectives on the right-hand side of your screen, so you didn't need to constantly open your quest log and check what you were supposed to be doing. This addition was inspired by another of the most popular addons of the time -- addons such as MonkeyQuest that provided exactly that functionality. The ability to remind yourself what you were working on and check your progress at a glance was something that absolutely did not exist when the game launched. It was a purely player-created initiative. Players also labeled the addition of such a feature as "dumbing down the game."

wow.curse.com has emerged as one of the main players when it comes to offering a platform for WoW AddOn developers and users alike. The domain is part of the Curse network, a commercial gaming network centering around MMO games. Developers can easily upload their programs, keep detailed change logs, add preview images and interact with gamers. In addition to regular HTTP downloads, the Curse Client offers an alternative means of comfortably getting all AddOns and their updates without having to visit the website.

Another notable AddOn download and developer site is wowinterface.com, which is part of the ZAM network (through MMOUI).

Bad reputation was gained in some circles by wowmatrix.com, a popular download/update manager, when their way of re-distributing AddOns without crediting the author or asking for permission was criticized. Additionally, WowMatrix had to start hosting the files on their own servers, after Curse and WowInterface blocked downloads from AddOn updaters. Both sides claim that the other party was unwilling to negotiate.