How to Fix “Asset is marked as don't save, but is included in the build” Warnings in Unity

This warning means a scene references an object flagged as ephemeral — the build keeps the reference but the object will not be there, becoming a missing reference at runtime. Here is the cleanup.

How to fix it

1. Find who references it

The warning names the object; search scenes and prefabs for fields holding it (procedural materials assigned in edit mode via scripts are the classic source).

2. Create runtime objects at runtime

If a script generates a mesh or material, do it in Awake/Start and assign it then — edit-mode creation plus serialization is the bug.

3. Promote genuine assets

If the object should ship, save it as a real asset (AssetDatabase.CreateAsset) and reference that instead of the DontSave instance.

4. Sweep with a validation script

An editor script that scans serialized fields for HideFlags.DontSave objects catches these before every build instead of as build-log noise.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.