port unity game to steam

Port a Unity game to Steam

A Unity to Steam port is a rebuild plus a store submission. No tool reads a Unity project and produces a finished Steam build.

Start the rebuild

Porting a Unity game to Steam means rebuilding a game you own in a new engine and then shipping that build through Steamworks. Summer Engine does not import .unity scenes, prefabs, or .unitypackage files.

The work splits in two. First the rebuild: scenes, gameplay logic, input, UI, and save data are re-authored in Summer Engine. Your art, audio, models, animations, and level layouts move across as files, because standard formats such as PNG, WAV, OGG, glTF, and FBX are not Unity specific. Second the store work: a Steamworks partner account, a depot, a build upload, and a store page that passes review.

Summer Engine is compatible with Godot 4 workflows and is a fully custom engine with more than a million lines of custom code. Games are written in C++ and GDScript, and C# works on every target except web. You can describe the game in plain language to generate a first pass, then edit the real project locally. You own the project and pay no royalties.

What transfers from a Unity project and what does not

Transfers: textures, sprites, audio files, 3D meshes in glTF or FBX, fonts, localization tables, spreadsheets of game data, and your level layouts as reference. Does not transfer: MonoBehaviour scripts as running code, prefab and scene serialization, Animator controllers, ScriptableObjects, Unity Timeline, the Unity input system bindings, and any Asset Store package whose license does not allow reuse outside Unity. Treat your C# scripts as an exact design document. They tell you every number the rebuild must match.

The Steamworks side, in order

Create a Steamworks partner account. Pay the one time app submission fee, currently 100 USD per title, which is recoupable against sales. Fill in the store page, age rating questionnaire, and tax and banking details. Create a depot per platform you ship. Upload builds with SteamPipe using a content builder script. Set a launch option pointing at your executable. Steam review checks the build runs and the store page is accurate, not that the game is good.

Desktop features Steam players expect

Steam builds need windowed and fullscreen modes, resolution and vsync options, remappable keyboard and mouse controls, and full gamepad support through Steam Input. Add cloud save support by writing saves to one known directory and declaring it in Steam Auto Cloud. Achievements and stats are defined in Steamworks and unlocked from your code. Plan the Steam Deck case early, since a Deck compatible build widens your audience at no extra cost.

How the rebuild goes fastest

Rebuild one vertical slice first: one level, one enemy, the player controller, the pause menu, and the save file. Match feel by copying exact values out of your Unity code, including move speed, gravity, jump height, and cooldowns. Once the slice feels like the original, content comes over quickly because the systems already exist. Use plain language requests in Summer Engine to draft each system, then tune the generated GDScript or C++ by hand.

Frequently asked questions

Can Summer Engine import a Unity project file?

No. There is no importer for .unity scenes, prefabs, or .unitypackage archives. You rebuild the game and bring across the asset files you own.

Will my C# scripts run after the port?

Not as Unity code, because they depend on the UnityEngine API. C# itself is supported in Summer Engine on desktop and all native targets, so the logic can be rewritten in C#, GDScript, or C++. Only web excludes C#.

How much does it cost to publish on Steam?

Steam charges a one time app submission fee of 100 USD per title, recoupable once the game earns 1000 USD. Valve then takes a revenue share on sales. Summer Engine charges no royalties on top of that.

Do I still need Unity installed?

Only to open the old project and export assets or read values. It is not needed to build or ship the Summer Engine version.

How long does a Unity to Steam port take?

It depends on systems, not on hours of content. A small 2D game with one player controller and a few enemy types is usually a few weeks of part time work. A large 3D game with custom tooling takes months. The vertical slice tells you the real number.

Can I keep selling the Unity build while porting?

Yes. You own the game, so the original build can stay for sale anywhere while the rebuild is in progress.

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Download Summer Engine, describe what you want, and watch it come together. Free to start, no coding required.

Start the rebuild

Port a Unity game to Steam

What transfers from a Unity project and what does not

The Steamworks side, in order

Desktop features Steam players expect

How the rebuild goes fastest

Frequently asked questions

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