When you look at most modern games, they’re built on familiar foundations—Unreal Engine, Unity, Godot. Pick an engine, learn it, build your game. But Hytale? That’s a different story entirely.
Hypixel Studios made what some might call a “crazy” decision early on: they built their own engine from scratch. We’re talking six-plus years of foundational work before we even see the game launch. But there’s a method to this madness, and in Summer 2024, they officially revealed the architecture that makes it all possible.
The Engine Reboot: From Java/C# to C++
Here’s the key moment in Hytale’s technical history: at some point during development, Hypixel Studios made the decision to completely reboot their engine. They switched from a Java-based server with a C# client to building both in C++.
According to the official Summer 2024 Technical Explainer, this decision was driven by three main goals:
- Multiplatform support — C++ makes it easier to release across multiple platforms
- Lower-spec device performance — The new engine could run better on less powerful hardware
- Long-term maintainability — A robust core engine they could patch and maintain for years
This wasn’t a failure; it was a calculated move to modernize their tech stack before launch. And it’s finally paying off—the Spring 2025 Development Update confirms that internal playtesting began in 2025 with core systems like movement, block placement, combat, and crafting all online.
Enter Flecs: The ECS Powering Hytale
The biggest technical shift in the reboot was adopting Flecs, an Entity Component System framework created by Sander Mertens. This is official—as confirmed in Hytale’s June 2024 technical blog post.
If you’re not familiar with ECS, here’s the simple version: instead of organizing code around objects (like “Enemy” or “Weapon”) using traditional object-oriented programming, you organize it around data. An entity is just a collection of components—data chunks—that define what it is and what it can do. Systems then process all entities that have specific component combinations.
The official blog explains it this way:
“Whereas in the entity-component model the functionality lives within the component itself, ECS decouples this functionality from the data and state it processes. Instead of having each component with its own internal update logic, we have systems which match entities with defined sets of components and act upon them.”
Why ECS Matters for Hytale
The benefits of this architecture go beyond just “cleaner code.” Here’s what Flecs actually enables:
1. Performance Through Data Locality
By keeping related data packed together in memory, the CPU can process it more efficiently. The blog explains this results in “significantly faster” performance compared to C# or Java implementations, with “smart implementation of parallelisation and multi-threading.”
2. NPCs That “Think” Faster
This is the most concrete example we have of Flecs in action. Hytale’s Combat Action Evaluator is a framework that allows NPCs to make intelligent decisions about which attacks to use and which targets to prioritize.
In the legacy Java engine, this had to run at “irregular intervals” because of performance concerns—the NPCs would make slower decisions that were “slow enough to be perceptible to the player.”
With Flecs? All those checks can happen simultaneously through parallelization. The blog puts it plainly: “In essence, this means that NPCs can think faster—reacting to changes in the environment and their surroundings much more responsively than they ever could have in the legacy engine.”
3. Modding Through Data-Driven Design
The blog explicitly calls out how ECS benefits modding:
“Not only does it facilitate highly data-driven functionality through asset configuration, where simply changing the components attached to an NPC or object results in markedly different behavior, but it theoretically allows for the creation of entirely new functionality without needing to tinker with existing code.”
That’s the promise—modders could create entirely new behaviors just by attaching different components, without writing deep code changes.
4. Flecs-Specific Features
Hypixel chose Flecs over other ECS frameworks for its extended features. One example mentioned is “relationships”—data that connects one entity to another. This enables powerful queries like “find me all entities that Like Entity B” or “find me all NPCs bearing swords that are aggressive to the player.”
The Legacy Engine’s ECS Implementation
Here’s something I didn’t know before reading the official post: Hytale’s legacy engine already had a homegrown ECS implementation, but it was Java-only and server-side. They learned from that experience—“implementing a robust and performant ECS framework from the ground up is an incredibly challenging and time-consuming endeavor.”
This is why they adopted Flecs rather than building their own again. As they put it, Flecs is “battle-tested, receives frequent updates and bugfixes, and with its comprehensive suite of tests, we can be relatively certain of its stability.”
What This Means for Players
The engine reboot and ECS adoption translates to several concrete benefits:
- More responsive combat — NPCs can react to player actions in real-time without artificial delays
- Larger worlds with more entities — The parallel processing enables thousands of active entities without performance degradation
- Better modding support — The data-driven architecture means modders can change game behavior through configuration rather than deep code changes
- Cross-platform potential — The C++ codebase makes porting to different platforms more feasible
The Road Forward
The Spring 2025 update confirms that “steady improvements across many areas of the engine are allowing us to bring an increasing number of gameplay systems online.” The rendering team has been “re-establishing—and in many cases improving upon—atmospheric features,” including better trees, shadowmaps, and skybox rendering.
The engine reboot is complete. The ECS is in place. Internal playtesting has begun. The question now isn’t whether the tech can support the vision—it’s how quickly the content can catch up.
And if the engine is any indication, Hypixel Studios is willing to take their time to get it right.