A free 3D browser-based city builder idle game in the style of Cities: Skylines
Build your own 3D city directly in your web browser, no download required
BuildCity is a free browser-based 3D city builder where you become the mayor of your own city. Place roads and public utilities, watch citizens settle in automatically, collect taxes, and grow your city over time. The game runs in any modern web browser without installation, and idle progress means your city keeps developing while you are away. With 5 to 10 minutes of daily play you can plan layouts, react to events, and steadily expand a small starter district into a thriving simulation that supports thousands of citizens.
The design goal is to keep the depth of a desktop city builder while removing the friction that usually comes with one. There is no client to install, no save-file management, and no long initial download. Open the site, sign up, and the first district can be running within a few minutes. Returning players see their city exactly where they left it, with idle income waiting to be reinvested into the next upgrade.
As mayor you place power plants, water intakes, wastewater plants, police stations, fire stations, parks, schools, and hospitals to build the city's infrastructure. Each service has a coverage radius, a build cost, an hourly upkeep, and a land value bonus. Choosing where to place each one matters more than how many you place. The buildings reference covers each one in detail.
Once power, water, and road access are connected, citizens settle automatically. Land value and density decide what kind of building appears, ranging from a 1x1 starter house to a 2x2 high-rise. The path to denser buildings runs through service coverage, parks, and clean utilities, not through any direct civilian-side action. You shape the conditions, the city shapes itself.
Fires, crime, and other random events can damage buildings if coverage is missing. Without a fire station nearby a building can burn down to an abandoned ruin, which means the lost income lasts longer than the event itself. Police prevents crime events on a separate track. Both stations together protect against the two main event categories that can erase city growth.
BuildCity is designed for short daily sessions, not marathon play. The city continues to generate income while you are away. Returning, collecting income, fixing one bottleneck, and planning the next district is the core loop. Five to ten minutes per session is enough to keep a city growing steadily over weeks or months.
BuildCity started as a personal project to test how far a browser-first 3D city simulation could go without giving up player depth. Early versions focused on getting the renderer, road system, and citizen settlement working together. Later milestones added the public city ranking, multilingual UI, and the strategy reference. The game continues to evolve with frequent updates rather than discrete releases, so players see new content and balance changes regularly.
The server side runs Spring Boot on Java 17 with JPA over MySQL. Spring Security protects authenticated routes and rate-limits sensitive actions. Thymeleaf handles server-side rendering for content pages and game entry, while the in-game client uses an ES module loader to keep startup fast.
The 3D client is built on Three.js with adaptive resolution scaling, instanced mesh pools for repeated buildings, and a memory-aware dispose policy for geometries, materials, and textures. Large 3D models are served from a CloudFront CDN with one-year immutable caching. A versioned cache key invalidates only the assets that actually changed between releases, which keeps most updates from triggering unnecessary downloads.
BuildCity runs in any modern browser. No download, no install, no client. Sign up and start building. The first district can be running within a few minutes, and an account keeps the city in sync across desktop and mobile.
Is BuildCity completely free? Yes. The full game loop including idle progress, public city pages, and rankings is available without payment. There is no required purchase to start a city or to grow it past any specific milestone.
What devices can run BuildCity? Any device with a modern browser. The renderer adapts to lower-end hardware automatically, so older laptops and mobile phones can still run a playable session. The same account works across devices, so a city started on desktop can be continued from a phone.
How is BuildCity different from a traditional city builder? Browser delivery, idle progress, and public city sharing change the rhythm of play. You do not commit to a long uninterrupted session. The city continues without you, and returning to fix one bottleneck per day is enough to grow a meaningful city over time. Public visit pages also turn the city into a shareable object instead of a private save file.
Will my city be deleted if I stop playing? No. Cities stay in the database as long as the account exists. Returning after a long break shows the same city with idle income accumulated.
Where does development go from here? The roadmap focuses on richer service mechanics, more building variety, deeper economy systems, and additional language coverage. Patch notes are visible from the home page and update with each release.
For service questions, bug reports, or feature suggestions, please reach out by email. Localised player support is available in English and Korean.