[1] Based upon the gameplay of the Age of Empires series, it was originally developed by Robot Entertainment, but on February 24, 2011, Gas Powered Games, took over production.

[2] The game was free-to-play—it was free for users to play, though premium content could be earned or purchased, such as access to special items and blueprints, and more quests and features.

On March 27, 2012, the game premiered on Steam after a major overhaul patch which addressed complaints of an "MMO-like grind" and many other features, along with the debut of the Celtic civilization.

Also, the game features a great quantity of new content, such as the ability to craft items with earned materials and trading with other players.

To assure victory, the player had to gather and preserve resources to spend on new units, buildings and more advanced technology.

Civilian units, called villagers, were used to gather resources (hunting, fishing, farming, forestry, mining etc.).

All military classes are developed to maintain a balance on gameplay, and thus avoiding visible advantages between civilizations.

Unique units are available for the Greek, Egyptian, Celts, and Persian civilizations, either from the start of the game or through advisor cards.

Buildings can research technologies and upgrades that increase economic, military or unit-based efficiency, as well as provide resources for the player.

Players can add buildings, rewards, houses as well as statues and bushes along with other things to decorate their capital city.

Standard PvP is the first option and allows the player to use star techs from their tech-tree as well as any gear and advisors that they have equipped in their capital city.

In this PvP option all gears, star techs and advisors are disabled and cannot be used to start the players off at an even footing.

All gears equipped will provide the units with a cosmetic change but will not affect their stats like they would normally do in PvE missions.

In Arena PvP, you can play against any human opponent in your party as well as choose the map and teams (if it is a 2v2 match) before starting the game.

Former Age of Empires II lead designer Ian M. Fischer stated: "When we started floating some of the early [AoEO] out to people other pieces fell into place – I cannot tell you how many times I have had someone email me or talk to me at a show and mention how much they loved the villagers carrying big hunks of meat in the original Age or the priest "wololo"".

From that point on, one of the goals was to invoke nostalgia from fans of the series when playing the game, despite the newer and updated features.

This resulted in a heavily modified version of the BANG engine used in previous games of the series, along with requiring large amounts of additional server code and infrastructure to be implemented.

In composing the music, Rickwood strove to keep it in the spirit of Stephen Rippy's and Kevin McMullan's work from the prior games of the series.

[18] On February 24, 2011, it was announced - first via Chris Taylor's Facebook page - that Gas Powered Games had taken over development from Robot Entertainment.

The Celts was postponed to March 2012, and was the first out of the four civilizations solely created from start to finish by Gas Powered Games since taking over development.

[22] On January 3, 2013, it was announced by AOEO Trajan (Kevin Perry) via the official community blog that Age of Empires Online had finished its development stage and was entering its support phase,[23] and in September 2013, Microsoft Studios announced that the Age of Empires Online servers would be shut down on July 1, 2014.

[24] Producer Kevin Perry gave a presentation at the 2013 Game Developers Conference explaining the reasons for AoEO's closure and why he believed its business model ultimately failed, that being mostly due to the content being too expensive to create for the small daily active userbase.

Justin Calvert of GameSpot gave the game a 6.5/10, noting the PvP matchmaking system, enemy AI, and pricing as weak points, but stated: "Age of Empires Online effectively infuses its conventional real-time strategy gameplay with massively multiplayer online-style loot and leveling mechanics.

"[37] PC Magazine gave the game 3.5 out of 5 stars, and complimented the in-game artwork as "well done" and "nicely scalable", but felt the free to play aspect should have offered more to the player.

Reviewer Matthew Murray wrote, "Age of Empires Online is highly enjoyable, and I found myself afflicted with one-more-turn-itis when a fiendish mission objective captivated (or frustrated) me.

"[44] GameSpy reviewer Mike Sharkey panned the game in his initial review,[48] but after the game received a major overhaul patch, he later stated: "Well, AoE Online is now on Steam, and courtesy of a massive spring patch, the vast majority of the problems I had with it have been addressed.

"[51] PC Gamer later summarized the game's major complaints during its initial launch and noted that many of them were addressed or improved by the developers.

[52] Age of Empires Online was the third most played Games for Windows Live title for the year 2012 based on unique users.