# buildStarted

> Event that is invoked on the main thread when the assembly build starts.

## Definition

* **Type:** Event
* **Namespace:** [UnityEditor.Compilation](/engine/6000.5/script-reference/unityeditor/compilation.md)
* **Assembly:** UnityEditor.CoreModule

> **Warning:**
>
> **Deprecated.** This feature is being deprecated and will be removed in the future. Similar functionality can be achieved using the Roslyn compiler

```csharp
public event Action<string> buildStarted
```