Roblox (/ˈroʊblɒks/ ^ⓘ ROH-bloks) is an online game platform and game creation system developed by Roblox Corporation that allows users to program and play games created by themselves or other users. It was created by David Baszucki and Erik Cassel in 2004, and released to the public in 2006. As of February 2025, the platform has reported an average of 85.3 million daily active users. According to the company, their monthly player base includes half of all American children under the age of 16.

The platform hosts millions of user-created games (officially referred to as "experiences"), all created using a dialect of the programming language Lua and the platform's game engine, Roblox Studio. While Roblox is free-to-play, it features in-game purchases done through its virtual currency known as "Robux", and game developers on the platform are able to create items that cost Robux. Furthermore, the platform hosts a large virtual economy centered around those items and Robux. Using the platform's "Developer Exchange" program, creators on the platform are able to exchange their earned Robux for real-world currency. The platform has also been used to host virtual concerts and events, as well as advergames.

While Roblox started off small—both in playerbase and as a company—it began to grow rapidly in the second half of the 2010s. This growth was further accelerated by the COVID-19 pandemic. By 2020, over 5,000 games on Roblox had been played over a million times, and over 20 had been played over one billion times. Although critic reviews for Roblox have been positive, it has faced heavy criticism for its content moderation, which in turn has led to a large amount of sexual or politically extremist material on the platform. It has also been criticized for its alleged exploitative practices toward children and microtransactions. The platform has been restricted or completely blocked in several countries, including China, Turkey, Qatar, and Jordan.

Roblox is an online game platform and game creation system built around user-generated content and games, officially referred to as "experiences". Games can be created by any user through the platform's game engine, Roblox Studio, and then shared to and played by other players. The games featured on Roblox vary in genre, from role-playing games to ones centered around escaping prison, among others. The platform is made to appeal to a family-friendly audience, and has been described as a massively multiplayer online game (MMO).

While Roblox is free-to-play, it features a virtual currency known as "Robux" that can be purchased with real-world money. Robux can be used to purchase virtual items that the player can use on their virtual character (or "avatar") on the platform, or access experiences that require payment. As with games, avatar items on Roblox are mainly user-generated, though most items on the platform were made by Roblox themselves for most of the platform's history. Through the platform's "Developer Exchange" program, creators on the platform are able to exchange their earned Robux to real-world money. In addition, Roblox features a monthly service called "Roblox Premium", with its subscribers gaining access to more features on the platform and a monthly stipend of Robux.

Roblox features a large virtual economy centered around Robux, its virtual currency. The currency allows users to buy, sell and create virtual items. Roblox also has a service called "Roblox Premium", a monthly subscription that gives users monthly stipends of Robux (with the amount depending on the selected subscription tier), discounts when purchasing items, more Robux being granted per purchase, and access to the item trading system.

Similarly to games, many items on Roblox are user-generated. While only Roblox developers were able to create avatar items early on, the capabilities of user-generated content has expanded greatly over time. Since 2019, select users have gained the ability to publish avatar accessories, animations, bundles and more. Some items on Roblox have a "limited" status, with only a few being available and the price of the item based on supply and demand rather than a fixed price. These items function similarly to non-fungible tokens. The prices of limited items range, with the most valuable ones costing millions of Robux. After the original supply of that item runs out, players can resell them for a higher price. Additionally, users with an active Roblox Premium subscription are able to trade limiteds amongst each other. Limited items made by the community cannot be traded and this feature is restricted to official items.

Developers on the platform are able to create purchasable content through one-time purchases. Through the Roblox "Developer Exchange" program, users are able to exchange their earned Robux for real-world money, as long as they have at least 30,000 Robux. In 2020, Roblox reported that roughly 345,000 game developers on the platform earned money through the program. Avatar item creators have also been able to generate profit with the platform, with some individuals designing items as a full-time job. It has been reported that the highest-earning creators have earned over $100,000 a year from item sales.