Unity Build Pipeline

Configure, script, and automate Unity 6.3 LTS player builds: scenes, platform target, scripting backend, stripping, and headless/CI builds. Targets Unity 6.3 LTS (6000.3).

When to use

• Use when setting up Build Settings/Profiles, choosing a platform and scripting backend (Mono vs IL2CPP), reducing build size with managed stripping, scripting a repeatable build with BuildPipeline.BuildPlayer, or wiring a CI/headless build.
• Use when the project has ProjectSettings/EditorBuildSettings.asset or a CI build script.

When not to use: authoring a CI service config end-to-end is DevOps; this skill covers the Unity-side build API and settings. Console/platform certification specifics are platform-NDA territory. Storefront submission → steam-publish / itch-publish.

Core workflow

1. List the scenes to build (File → Build Profiles → Scene List, or EditorBuildSettings.scenes). Only listed, enabled scenes ship; scene 0 is the start scene. A Build Profile asset can carry its own Scene List (Add Settings → Scene List); when it does, that profile builds its list, not the global one.
2. Pick the platform target and switch the active build target if needed (BuildTarget / EditorUserBuildSettings). In batch mode, pass -buildTarget <name> on the command line instead: SwitchActiveBuildTarget is not available there.
3. Choose the scripting backend (Player Settings): Mono (fast iteration, desktop) vs IL2CPP (AOT C++; required for many platforms, better perf, harder to reverse). IL2CPP needs the platform's C++ toolchain installed. (Forward note: Unity is developing a CoreCLR backend as a modern .NET runtime successor to Mono, but in the Unity 6.7 beta it is still experimental, desktop-only, and documented as not suitable for production — so for 6.3 LTS the choice stays Mono vs IL2CPP.)
4. Tune size/perf: set Managed Stripping Level (Disabled → Minimal → Low → Medium → High) and protect reflection-only code with a link.xml. Set Quality Settings per platform.
5. Script the build with BuildPipeline.BuildPlayer(BuildPlayerOptions) and inspect the returned BuildReport — a non-Succeeded result must fail your pipeline.
6. Run headless for CI with -batchmode -quit -executeMethod, and check the exit code.
7. Verify the actual output runs (launch the player), not just that the build returned without throwing.

Patterns

1. Scripted build with a result check

using UnityEditor;
using UnityEditor.Build.Reporting;
using UnityEngine;

public static class BuildScript
{
    [MenuItem("Build/Windows x64")]
    public static void BuildWindows()
    {
        var options = new BuildPlayerOptions
        {
            scenes = new[] { "Assets/Scenes/Main.unity", "Assets/Scenes/Level1.unity" },
            locationPathName = "Builds/Windows/Game.exe",
            target = BuildTarget.StandaloneWindows64,
            options = BuildOptions.None,            // add BuildOptions.Development for a dev build
        };

        BuildReport report = BuildPipeline.BuildPlayer(options);
        BuildSummary summary = report.summary;

        if (summary.result != BuildResult.Succeeded)
            throw new System.Exception($"Build failed: {summary.totalErrors} errors");
        Debug.Log($"Build OK: {summary.totalSize} bytes in {summary.totalTime}");
    }
}

2. Headless / CI invocation

# Exit code is 0 on success; -quit ensures the editor closes; -nographics for build servers.
# -buildTarget makes the Editor start on that platform, so scripts compile with its defines.
Unity -batchmode -quit -nographics \
  -projectPath "/path/to/Project" \
  -buildTarget win64 \
  -executeMethod BuildScript.BuildWindows \
  -logFile -

3. Build a saved Build Profile

using UnityEditor;
using UnityEditor.Build.Profile;
using UnityEditor.Build.Reporting;

public static class ProfileBuild
{
    [MenuItem("Build/Windows Release Profile")]
    public static void Build()
    {
        var profile = AssetDatabase.LoadAssetAtPath<BuildProfile>(
            "Assets/Settings/Build Profiles/WindowsRelease.asset");
        var options = new BuildPlayerWithProfileOptions
        {
            buildProfile = profile,                 // platform, scene list, defines from the asset
            locationPathName = "Builds/Windows/Game.exe",
            options = BuildOptions.None,
        };
        BuildReport report = BuildPipeline.BuildPlayer(options);
        if (report.summary.result != BuildResult.Succeeded)
            throw new System.Exception($"Build failed: {report.summary.totalErrors} errors");
    }
}

4. Protect stripped code with link.xml

<!-- Assets/link.xml — keep types the linker can't see are used (reflection, JSON, plugins). -->
<linker>
  <assembly fullname="MyGameRuntime" preserve="all"/>
</linker>

Pitfalls

• A scene loads in the Editor but is missing in the build — it isn't in the scene list (File → Build Profiles → Scene List, or the built profile's own list) or is disabled. SceneManager.LoadScene only sees listed scenes.
• IL2CPP build fails on a fresh machine — the platform C++ toolchain (e.g. Windows build tools, Android NDK) isn't installed. Mono has no such requirement.
• MissingMethodException/TypeLoadException only in the build — managed stripping removed reflection-only code. Lower the stripping level or add a link.xml preserve entry.
• Treating "BuildPlayer returned" as success — always check BuildReport.summary.result; it can return with errors.
• Addressables content is stale/missing — Addressables (com.unity.addressables) content is built by Build → Addressables or by AddressableAssetSettings.BuildPlayerContent. The Build Addressables on Player Build setting can do it during a player build, but when it is left at "Use global Settings" the result depends on each machine's Preferences — call the content build explicitly in CI, and check the profile's load path.
• The build platform's code didn't compile in — a scripted BuildPlayer for a target other than the active one keeps the active platform's UNITY_* defines, and define changes only apply after a domain reload. Switch platform first (in the Editor) or launch with -buildTarget (batch mode).
• Build ignores scenes you added to the global list — the Build Profile you build has its own Scene List. Edit that list; a profile without a Scene List uses the global one.
• Shipping a Development build — BuildOptions.Development enables the profiler/debugging and is slower; use BuildOptions.None for release.

References

• For a complete multi-platform CI build script (-buildTarget per platform, version stamping, argument parsing, exit codes), building a Build Profile from the command line, and an Addressables content-build call, read references/ci-build-script.md.
• Primary docs: ScriptReference/BuildPipeline.BuildPlayer, ScriptReference/BuildPlayerWithProfileOptions, the Manual pages "Editor command line arguments" and "Manage scenes in a build", and Unity Manual build sections (player settings, managed code stripping). For the forward-looking CoreCLR backend, see the experimental note at https://docs.unity3d.com/6000.7/Documentation/Manual/scripting-backends-coreclr.html.

Related skills

• steam-publish / itch-publish — distributing the player you just built.
• unity-csharp-scripting — editor scripting conventions used by build scripts.