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Use an Editor-side audit that checks every prefab asset and each GameObject it contains. Unity’s GameObjectUtility.GetMonoBehavioursWithMissingScriptCount reports missing MonoBehaviour scripts per GameObject; it does not scan an entire project by itself. Record the prefab path and object hierarchy for every nonzero result, then investigate before removing anything. Treat the report as a pre-build integrity check, not proof that every missing script will break a build.
What the prefab scan detects—and what it does not
Unity 6.0 documents GameObjectUtility.GetMonoBehavioursWithMissingScriptCount(GameObject) as getting “the number of MonoBehaviours with a missing script for the given GameObject.” The method belongs to UnityEditor, so put the audit in editor tooling rather than runtime code. Confirm the API exists in the Unity editor version your project uses before making the check a required CI step. Unity 6.0 GameObjectUtility scripting API
The method answers a per-GameObject question. A project-wide prefab audit must enumerate prefab asset paths, load or traverse each asset’s GameObjects, and call the method on each one. That traversal is your editor tool’s responsibility; Unity’s cited API page does not provide a single project-wide scan call. Log the asset path, hierarchy path (for example, Root/Visuals/Weapon), and count so a developer can locate the affected object.
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Build a repeatable Editor audit
- Start from a clean, version-controlled working tree. Save the scan output separately from the assets being checked, and make the initial run report-only.
- Enumerate prefab asset paths. Use the project’s AssetDatabase workflow to find candidate prefab assets. Include nested prefab assets explicitly; do not assume that checking a parent also checks every nested asset.
- Inspect the GameObjects in each prefab. Traverse the prefab contents and call
GameObjectUtility.GetMonoBehavioursWithMissingScriptCount(go)for every GameObject. Record only results greater than zero, along with the prefab path and hierarchy location. - Run the separate checks below. They cover missing managed-reference types, unloadable ScriptableObject instances, and missing prefab source assets; none replaces the GameObject scan.
- Review and repair findings. Restore or correctly reattach a missing type where possible. Remove a missing component only after confirming it is obsolete.
- Repeat before building. Retain the report or make the preflight fail on findings according to your team’s policy.
This is an implementation pattern assembled around Unity’s per-object API, not a prescribed project scanner. The precise asset enumeration and prefab traversal should be tested in the project’s installed editor version and against its prefab setup.
Run the related checks separately
| Check | What it detects | Scope and caveat |
|---|---|---|
GameObjectUtility.GetMonoBehavioursWithMissingScriptCount |
Missing MonoBehaviour scripts attached to a GameObject | Per GameObject; your tool must enumerate prefab assets and traverse their contents. Unity 6.0 API |
PrefabUtility.HasManagedReferencesWithMissingTypes |
Missing [SerializeReference] managed-reference types |
Checks the prefab asset directly and excludes nested prefabs. Applying property modifications can erase missing-type information; Unity says editing in Prefab Mode preserves it. Unity API reference |
AssetDatabase.GetScriptableObjectsWithMissingScriptCount |
Unloadable ScriptableObject instances | Takes an asset path and works only with native asset files; Unity documents that passing a non-native asset file throws an exception. Unity API reference |
PrefabUtility.IsPrefabAssetMissing |
Whether an object belongs to a prefab instance whose source asset is missing | Checks the source relationship, not a missing component script. Unity API reference |
Investigate a finding before cleanup
A missing component is a clue to investigate, not an instruction to delete. Possible causes include a deleted or renamed script, unavailable package or source content, or a source-control merge or revert that left the asset and code out of sync. Unity specifically identifies deleting a type script or moving or renaming it without its .meta file as causes of unloadable ScriptableObject instances. Unity’s ScriptableObject API reference
- Check whether the script or package that defines the type is present and whether its GUID-bearing
.metafile stayed with it. - Review recent renames, moves, merges, reverts, and package changes for an interrupted asset/code change.
- If the original type is available, restore it or repair the reference and rerun the audit.
- If the component is confirmed obsolete, remove it deliberately and review the prefab change in version control.
Unity exposes GameObjectUtility.RemoveMonoBehavioursWithMissingScript(GameObject), but the existence of a removal method does not establish that every missing component is safe to discard. Keep discovery and cleanup as separate actions. Unity 6.0 GameObjectUtility scripting API
Why this belongs in a build preflight
Unity documents prefab assets with missing scripts as an example of assets that cannot have overrides applied. That makes findings relevant to prefab integrity and justifies checking before a build, but it does not mean every missing script necessarily causes a build failure. Unity API reference
After developers review a report, a team can choose to keep the scan advisory or fail a preflight when approved policy conditions are met. Keep the output actionable and retain enough context to reproduce and resolve each finding. Unity’s cited API documentation defines detection behavior; it does not quantify how often missing scripts break builds or how long repairs take.
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