The Armory was a searchable database of information for World of Warcraft. Since the Armory pulled its data from the actual game servers, it was the most comprehensive database on the characters, arena teams, and guilds of World of Warcraft in existence.
While the Armory data got automatically updated, it was not a quite suitable replacement for traditional, non-"live" character databases. This is because it only saved a character's status after their last logout, so there was no way to display multiple sets of gear (for instance healing, PvP, or resistance sets) or the effects of different talent builds.
When the Armory first came up, many players were concerned that their items and stats were viewable for all to see. This was the core of Blizzard's Tinfoil Hat April Fool's joke.
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