Defold vs Unity for web and mobile games

Short answer: which engine should you choose?

Choose Defold when the game is 2D or light 3D, has to load fast in a browser, a playable ad or a messenger platform, and must run smoothly on cheap Android phones. Choose Unity when the game is built around rich 3D, needs a specific Unity-only SDK or Asset Store package, or will be maintained by a team that already works in C# and Unity. Both engines can ship to web, iOS and Android, so the real question is which trade-offs your project can accept.

I have worked with game engines for over 13 years, and at Codeward we use Defold as our core engine while still supporting selected Unity projects. This comparison is written from that practical point of view: what each engine costs you in download size, performance, licensing risk and team time.

Build size and loading time on the web

For web games, size is not a technical detail. Every extra megabyte means more players who close the tab before the first screen appears, especially on mobile data. Game portals, ad networks and platforms such as Facebook Instant Games publish their own limits and recommendations for size and start-up time.

• Defold. The engine is small by design. The Defold team publishes a public build size dashboard for every release and platform. For version 1.13.2 the optimized web engine (WebAssembly) is about 2.4 MB before compression, and forum measurements of an empty project show a download of roughly 1 MB after the server compresses it. Unused modules can be removed with an app manifest, which makes the build smaller still.
• Unity. Unity can export to the web (WebGL, now called the Web platform in Unity 6), and recent versions improved support for mobile browsers. The baseline runtime is larger, though, and a Unity web build usually needs more tuning (code stripping, compression, asset bundles) to reach the same start-up time as a small Defold build.

Your art is usually larger than either engine. Texture compression, atlases, audio formats and loading content in stages decide the final size in both engines. Read more about this in our guide to Defold for HTML5 games.

Performance on low-end phones

Many players use budget Android phones with little memory and weak GPUs. A game that runs well on a developer’s flagship phone can stutter, overheat or crash on the devices your audience actually has.

• Defold has a lightweight runtime written in C++ with game logic in Lua. A small memory footprint and a simple rendering pipeline help 2D games keep a stable frame rate on older devices and in mobile browsers.
• Unity can also run well on low-end phones, and many successful mobile games prove it. It usually takes more deliberate work: choosing the right render pipeline, limiting garbage collection spikes in C# code and keeping the build lean.

In both engines, test on real target devices early. Performance problems found in the last week before launch are the most expensive ones.

2D vs 3D

• 2D games. Defold was built with 2D in mind: sprites, atlases, tile maps, GUI, particles and Spine animations are first-class features. Puzzle, casual, hyper-casual, card, idle and arcade games are a natural fit.
• 3D games. Defold supports 3D models, cameras and custom shaders, which is enough for stylized or light 3D. Unity offers a much larger 3D toolset: advanced lighting, terrain, animation tools, visual effects and a big asset ecosystem. For a 3D-heavy game, Unity (or another 3D-focused engine) is usually the better choice.

Licensing and pricing: what changed at Unity

In September 2023 Unity announced a Runtime Fee: a charge per game install above certain revenue and install thresholds. The developer community reacted strongly, because the fee would have applied to games already in development and made costs hard to predict. Unity revised the plan within weeks, but trust was damaged.

On 12 September 2024 Unity cancelled the Runtime Fee for games and returned to seat-based subscriptions. According to Unity’s announcement:

• Unity Personal stays free for companies with up to 200,000 USD in annual revenue and funding (raised from 100,000 USD with Unity 6), and the “Made with Unity” splash screen became optional for Unity 6 Personal games.
• Unity Pro rose by 8% to 2,200 USD per seat per year from 1 January 2025 and is required above 200,000 USD in annual revenue and funding.
• Unity Enterprise rose by 25% and is required above 25 million USD.

For most small studios and brands this pricing is predictable again. The lesson from 2023 is still useful, though: with a commercial engine, the vendor can change the terms, so check the current pricing before each new project.

Defold is free to use, with no royalties, seat fees or runtime fees. Its source code is available on GitHub under the Defold License, a source-available license based on Apache 2.0. The engine was created at King and since 2020 has been developed by the independent, non-profit Defold Foundation, funded by partners and community donations.

Workflow, languages and tools

The daily workflow matters as much as the runtime, because it decides how fast your team can iterate.

• Languages. Unity uses C#, a popular, strongly typed language with excellent IDE support. Defold uses Lua for game logic, a small scripting language that is quick to learn, plus native extensions in C++ when you need platform code or extra performance.
• Editor and iteration. Defold has a compact editor with hot reload of code and assets on a running game, also on a connected phone. Unity has a much larger editor with visual tools for animation, lighting, timelines and level design.
• Extensions and SDKs. Unity has the Asset Store and SDKs from almost every ad, analytics and platform provider. Defold has an asset portal with community and official extensions for common services such as ads, purchases, Firebase and web game portals. Check your required SDKs for both engines before you decide.
• Builds. Defold can bundle for every platform from the editor, using a cloud build server for native extensions, so you do not need to install a separate SDK for each platform. Unity needs platform modules and local toolchains for each target.
• Engine updates. Defold releases a new version roughly every month and keeps project changes small between versions. Unity releases larger versions, and upgrading a big project between major releases can take planned time.

Community matters too. Unity has a huge base of tutorials, courses and forum answers. The Defold community is smaller but very active: on the forum and Discord the engine developers themselves often answer, and the documentation and examples focus on practical problems of web and mobile games.

When is Unity the better choice?

• 3D-first games. Games that depend on advanced 3D rendering, physics or large 3D scenes.
• Unity-only SDKs. When a key partner SDK, middleware or Asset Store package exists only for Unity and there is no reasonable alternative.
• An existing Unity team. If your developers know C# and Unity and will maintain the game for years, staying in Unity can be cheaper overall.
• XR and specialized platforms. Unity has broad support for VR, AR and other specialized hardware.
• Hiring. There are many Unity developers on the market, which matters if you plan to build an in-house team.

When is Defold the better choice?

• Web and HTML5 games. Small builds and fast loading on game portals, campaign pages and messenger platforms.
• Playable ads. Ad networks enforce strict size limits, and every second of loading costs conversions. See our guide to playable ads for mobile games.
• Mobile games for a wide audience. Casual and 2D games that must run smoothly on budget Android phones.
• One codebase for many platforms. HTML5, iOS, Android, Windows, macOS, Linux and, for registered developers, consoles from the same project.
• Predictable costs. No license fees now and no risk of runtime fees later.

Porting a Unity game to Defold

Some teams already have a Unity game and want a lighter web version, a faster mobile build or lower engine costs. A port from Unity to Defold is not an automatic conversion. The C# code is rewritten in Lua, and scenes and UI are rebuilt in Defold. Most of the assets can be reused: sprites, textures, audio, fonts, Spine animations and, in many cases, 3D models.

At Codeward a Unity-to-Defold port usually looks like this:

1. Audit. We review the Unity project, the build and the list of SDKs, and identify the riskiest parts.
2. Prototype. We port the core loop and one level, and measure size, loading time and frame rate on your target devices.
3. Port. We move the remaining features, content and integrations (ads, analytics, leaderboards, purchases) in milestones with playable builds.
4. QA and release. We test on target phones and browsers and help with portal and store submissions.

Porting makes the most sense for 2D and light 3D games where web reach, size or performance on low-end phones matter. If your game is a heavy 3D title, we will tell you honestly that staying in Unity and optimizing it may be the better option. Read more in our guide to porting a mobile game to web, or send us your Unity project details for a free first assessment.

How to decide for your project

Before choosing an engine, answer these questions:

1. Where will players open the game: a browser, an ad, an app store, Steam?
2. What download size and loading time does the platform or campaign accept?
3. Is the game 2D, light 3D or 3D-heavy?
4. Which SDKs and services must be integrated?
5. Who will maintain the game after launch, and in which language does that team work?
6. What is the budget for engine licenses over the lifetime of the game?

If the answers point to the web, mobile, 2D and tight size limits, Defold is very likely the better fit. If they point to rich 3D, a Unity team and Unity-only tools, choose Unity. When the answer is not obvious, a short prototype in the chosen engine is the cheapest way to find out.

About the author

Paweł Jarosz is a game developer in Kraków with over 13 years of experience, the founder of Codeward and Community & Content Manager at the Defold Foundation. He builds games and shares practical tutorials on the Unfolding Gamedev YouTube channel.