# Mouse0

> The Left (or primary) mouse button.

## Definition

* **Type:** Field
* **Namespace:** [UnityEngine](/engine/6000.7/script-reference/unityengine.md)
* **Assembly:** UnityEngine.CoreModule

```csharp
Mouse0 = 323
```

### Remarks

Use this to detect left mouse button presses. The “0” mouse button is the main button on the user’s mouse, which is usually the left mouse button.