Age of Empires Online has its own dedicated wiki here.
Age of Empires Online is a real-time strategy game developed by Robot Entertainment and Gas Powered Games and published by Xbox Game Studios, and was released on August 16, 2011. On January 3, 2013, Microsoft ceased further development on the game. A Microsoft representative later announced on the forums that on August 22, 2013, the Games for Windows – Live Marketplace would be shut down, leaving the game only accessible by current or former players. In September 2013, it was announced that the game would remain functional until July 1, 2014 when the service would be shut down. The closure was due to the content being too expensive to maintain.
In 2017, Age of Empires Online was relaunched using Microsoft's publicly released developer kit for the game and is now hosted on a server emulator known as Project Celeste. The game can be played for free in single-player and multiplayer mode with all online features fully enabled. In May of 2019, the team announced that they are developing Microsoft's unreleased Roman civilization for play based upon all known data of the civilization before the official servers were closed. The Romans were released on March 14, 2021.
Much like other games in the series, players develop a civilization while progressing through four Ages. These are the Copper Age, Bronze Age, Silver Age, and Golden Age. The player must use Villagers to gather resources (food, wood, gold, and stone) which are required to advance through the Ages, research new technologies, construct buildings and train units. Food is gathered by hunting animals, fishing, gathering berries, and farming. Wood is gathered by chopping trees. Gold and stone are both gathered by mining from limited deposits. An infinite supply of gold can be produced by trading from the Market or Dock, and all resources can be exchanged at the Market.
The game also has the new addition of massive multiplayer online gaming elements. The player possesses a Capital City for each started civilization, that continues to exist when the player is offline. Also featured is a crafting system, with the ability to craft items with earned materials, trading items with other players, live chat, and cooperative multiplayer quests.
The Capital City is similar to the Home City in Age of Empires III, in that it functions as a home base for the player's civilization. However, unlike the Home City, the Capital City is completely customizable by the player. The Capital City continues to exist even when the player has logged out of the game and can be visited, though not attacked or altered, by other players. The player can use the Capital City to manage quests, improve technologies, send mail, craft items, trade with other players, purchase and equip new gear for units, visit other player's cities, and visit AI controlled cities. When first starting, the Capital City will only have some buildings that are used to obtain quests, upgrade the player's civilization, and purchase material and consumable items. As the player progresses through the game, they will be able to place buildings, rewards, houses, statues, bushes, and decorations anywhere in their city.
Like other games in the series, Age of Empires Online contains a variety of civilian and military units. Economic units perform jobs such as harvesting resources, constructing buildings, or trading. Infantry use melee combat to attack at short range. Archers have a ranged attack that allows them to damage other units at a distance. Cavalry are mounted units with higher movement speed than other units. Siege units are slow, expensive units that deal high amounts of damage and are most effective against buildings. Priests are a special kind of military unit that instead of directly attacking, has the ability to convert enemy units to the player's civilization and to heal allied units. Naval units are units that can only travel over water and can be further broken down into two categories: Economic and Warship.
The buildings in Age of Empires Online can be categorized as economic buildings, military buildings or defensive structures. Each civilization has unique buildings that others do not, but some are common for all civilizations. The Town Center is the most important economic building in the game. The Town Center trains Villagers, provides population support, fires arrows at enemy units, and is where the player can advance to the next age. Other economic buildings can be built to improve Villager gathering, support population, or produce resources. Military buildings are used to train military units or to research military specific technologies; increasing their strength, defensive capabilities, or other attributes.
Players choose to play as one of six civilizations, three of which start at level 20 without their own dedicated story quests.
In May, 2019, the Project Celeste team announced their plans to release the Roman civilization that was under development before the game was originally shut down.
Quests are the main PvE aspect of the game and are similar to the campaigns of previous Age of Empires titles. Quests are given by NPCs in cities and completed by returning to the same NPC who assigned it after the objectives are complete. Rewards vary based on level, difficulty, and type. Certain quests also have a co-op option, which allows the player to do the quest with another player to help them. Each civilization has different quest lines, with unique quests that the other civilizations do not possess.
Age of Empires Online was the first game developed by Robot Entertainment, a company founded by former employees of Ensemble Studios. During early production, the game was originally called Age of Empires IV. In February, 2011, Gas Powered Games had taken over development from Robot Entertainment. Gas Powered Games was already working on the game, creating content packs and moving to take over as the lead developers. The game was released on August 16, 2011 with the Greek and Egyptian civilizations, followed by the Persians. The Celts, who were released March 2012, were the first of four civilizations solely created from start to finish by Gas Powered Games. On January 3, 2013, it was announced via the official community blog that Age of Empires Online servers would be shut down on July 1, 2014, mostly due to the content being too expensive to create for the small daily active userbase.
Age of Empires Online was republished in 2017 under a non-commercial license under Microsoft's "Game Content Usage Rules" by an independent group of developers and can be played for free on a server emulator known as Project Celeste with all online features fully enabled. The team uses Microsoft's publicly released development-kit to make balance changes, perform bug fixes, and expand the content where Microsoft's team left off. 
|Age of Empires|
|Age of Empires||The Rise of Rome · Definitive Edition|
|Age of Empires II||The Conquerors · The Forgotten · The African Kingdoms · Rise of the Rajas · Definitive Edition (The Last Khans) · Lords of the West · Dawn of the Dukes|
|Age of Empires III||The WarChiefs · The Asian Dynasties · Definitive Edition · The African Royals|
|Age of Mythology||The Titans · Tale of the Dragon|
|Age of Empires IV|
|Age of Empires Online · Age of Empires: Castle Siege|
|Handheld||Age of Empires: The Age of Kings · Age of Empires: Mythologies|
|Mobile||Age of Empires II Mobile (Deluxe) · Age of Empires III Mobile · Age of Empires III: The Asian Dynasties Mobile · Age of Empires: World Domination|
|Tabletop||Age of Empires: Expandable Card Game · Age of Mythology: The Boardgame · Glenn Drover's Empires: The Age of Discovery|