Separate the failure into stages before changing settings or code: does the project open, does the Player build, does it launch on the target, or does it run poorly after launch? Check the first relevant error in the Console or the appropriate log, then work through the target, build support, scenes, and tests. A successful build that will not launch needs a different investigation from a build that never finishes.
First, identify where the failure happens
“Build” and “run” are separate steps in Unity. Build creates a Player; Build and Run creates it and then opens it on the selected target. Record the exact Unity Editor version, target platform, whether the Editor opens the project, which step fails, and the first relevant error with its surrounding context. These details determine which requirements and logs apply; an isolated final error or a generic “try upgrading Unity” is not enough to identify the cause.
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- Project import or Editor compile: The project cannot open or compile in the Editor. Start with the Editor Console and Editor log.
- Player build: The Editor opens, but creating the Player fails. Check build support, scenes, target settings, and the build error.
- Player launch: The build completes, but the Player will not start on the selected device, browser, or computer. Use that target’s runtime logs.
- Runtime performance: The Player starts but runs badly. This is a performance investigation, not a failed build.
Check version and machine compatibility
Use the requirements for the specific Unity Editor release and Player target, rather than assuming one set of requirements applies to all Unity versions. Unity documents Editor requirements separately from Player requirements. For example, Unity’s Unity 6.0 system requirements list Windows 10 version 21H1 (build 19043) or newer for the Windows Editor, macOS Big Sur 11 or newer for the macOS Editor, and Ubuntu 22.04 or 24.04 for Linux Editor use. The same page recommends at least 8 GB of RAM for the Unity 6.0 Editor and notes that larger or more complex projects may need more. These are Unity 6.0 requirements, not universal minimums for every release or target.
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Install the target’s build support
Confirm that the Editor installation includes build support for the platform you selected. Unity’s Platform Browser documentation explains that Unity identifies when platform build support is absent and provides an install route through Unity Hub. Restart the Editor after installing a module, then check whether the target is available and attempt the build again.
Verify scenes and target settings
In the Build Settings window, make sure the intended scenes appear under Scenes in Build, are enabled, and belong to the build you mean to make. If the list is empty, Unity’s Build Settings documentation describes adding open scenes. Confirm that the selected target and its target-specific options match the device or platform where you intend to test.
Use Build to check whether Unity can create the Player. Use Build and Run when you also want Unity to launch that Player on the selected target. If Build succeeds but Build and Run fails, retain the successful build result as a clue and investigate launch and target logs rather than treating it as the same build error.
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Find the useful error in the right log
Start with the first relevant error and the lines around it, not just the last message shown after a long build. The Console can open the Editor log, and Unity’s log files documentation covers logs for the Editor, Package Manager, licensing, development Players, and Hub.
For failures after launch, look at the log for the actual runtime environment:
- Android: Check the device output in logcat.
- WebGL: Check the browser’s JavaScript console.
- Windows Player: Check
AppDataLocalLowCompanyNameProductNamePlayer.logunder the user profile, substituting the company and product names used by the project. - macOS and Linux Players: Use the user log locations described in Unity’s log files documentation.
Keep the complete relevant error and surrounding output when comparing attempts. A cropped message can omit the earlier cause or the context that distinguishes a build problem from a runtime one.
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Reproduce the build consistently
If the issue is intermittent or needs a repeatable check, run the build from the command line with the same project and target configuration as the failing Editor build. Unity’s command-line arguments documentation identifies -projectPath and -quit as required build arguments and recommends using -batchmode, -logFile, and either -buildTarget or -activeBuildProfile.
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Use the project path and target configuration that match the failure, and save the output log. This makes it possible to compare runs and see whether the failure occurs in a consistent, non-interactive invocation; it does not by itself identify or fix the underlying error.
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Test Editor logic separately from target behavior
Unity’s Test Framework supports Edit Mode and Play Mode tests. Use Edit Mode tests for logic that can be verified in the Editor and Play Mode tests for behavior that depends on runtime execution. Make sure test assemblies reference the code under test and the required test assemblies; setup details can vary with the project’s package and Editor versions.
When the question is whether a particular target Player launches or behaves correctly on its platform, test a Player on that target as well. Passing an Editor test does not establish that a built Player will launch successfully in a device, browser, or operating system environment.
Profile only after the Player runs
If the Player launches but has performance problems, use the Unity Profiler to investigate runtime behavior. Unity’s Profiler documentation describes attaching to a running Player built with Development Build enabled. Profiling cannot resolve a build that never completes or a Player that does not start.
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If the failure remains unresolved, share the details that let someone reproduce the same diagnostic path:
- Unity Editor version and target platform.
- Whether the Editor opens the project, whether Build completes, and whether the Player launches.
- The first relevant error and the surrounding Console or log output.
- Whether platform build support is installed and which target configuration is selected.
- For a launch failure, the relevant device, browser, or Player log; for a repeatability check, the command-line log and target arguments.
Without the project’s version, target, complete error output, and relevant Editor or Player logs, a specific code or settings fix cannot be established reliably.
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