# Layer-based collision detection

> Use layers to define which GameObjects can collide with each other.

Layer-based collision detection is a way to make a GameObject collide with another GameObject that's set up on a specific layer or layers.


**Layer Collision Matrix selected in the Project Settings window.:**
![](/api/media?file=/engine/6000.3/media/images/layer-collision-matrix.png)

The Layer Collision Matrix defines which GameObjects can collide with which Layers. To open the Layer Collision Matrix go to **Edit > Project Settings > Physics**.

In the image, the Layer Collision Matrix is set up so that only GameObjects that belong to the same layer can collide:

* Layer 1 is checked for Layer 1 only
* Layer 2 is checked for Layer 2 only
* Layer 3 is checked for Layer 3 only

If, for example, you want Layer 1 to collide with Layer 2 and 3, but not with Layer 1, find the row for **Layer 1**, then check the boxes for the **Layer 2** and **Layer 3** columns, and leave the **Layer 1** column checkbox blank.

## Set up layer-based collision detection

1. Select the GameObject you want to assign a layer to.

2. In the Inspector, select the **Layer** dropdown at the top, and either choose a Layer or add a new Layer. Repeat for each GameObject until you have finished assigning your GameObjects to Layers.


   **Cube selected in the Inspector, with Layer 1 assigned to it.:**
   ![](/api/media?file=/engine/6000.3/media/images/layer-collision-selection.png)

3. In the Unity menu bar, go to **Edit** > Editor, then select the **Physics** category to open the [Physics](/engine/6000.3/manual/unity-editor/editor-settings-reference/comp-manager-group/class-physics-manager.md) window.

4. Select the layers on the Collision Matrix that you want to interact with the other layers.

## Additional resources

* [Essential Unity concepts](https://learn.unity.com/pathway/unity-essentials)
* [Tags and layers](/engine/6000.3/manual/unity-editor/editor-settings-reference/comp-manager-group/class-tag-manager.md)
* [Collision detection](/engine/6000.3/manual/physics-section/physics-overview/collision-section/collision-detection.md)
* [Layers](/engine/6000.3/manual/working-with-gameobjects/layers.md)