# Optimize 2D lights with batching in URP

> Understand how to use the Light Batching Debugger to check how Unity batches lights.

Organize your 2D lights so Unity uses fewer textures to render light and shadows.

If two or more [sorting layers](/engine/6000.0/manual/unity2d/sprite/sort-sprites/sorting-group-reference.md) of GameObjects need exactly the same lights, Unity can render them using a single light texture and shadow texture instead of multiple textures. This process is called light batching and improves performance. For more information about light and shadow textures, refer to [Introduction to 2D lighting](/engine/6000.0/manual/unity2d/2d-urp/2d-index/lights-2d-intro.md).

## Batch lights and shadows

To merge two batches by making sure they use exactly the same lights, use the **Light Batching Debugger** window.

Follow these steps:

1. From the main menu, select **Window** > **2D** > **Light Batching Debugger**.
2. In the left-hand panel, select two batches to check how the 2D lights and shadows differ between the two batches.
3. Select each light in the **Lights** list, then set its **Target Sorting Layers** property to match the **Layer Names**.
4. Select each GameObject in the **Shadow Casters** list, then, in its **Shadow Caster 2D** component, set its **Target Sorting Layers** property to match the **Layer Names**.

For example, in the screenshot in the [Light Batching Debugger window reference](#lighting-batching-debugger-window-reference) section, **Light A** exists in **Batch 0** but not in **Batch 1**. To merge the batches, set the **Target Sorting Layers** of **Light A** to both the **BG** and **Default** layers.

## Minimize render textures

To reduce how much Unity writes to light and shadow textures, use one or more of the following approaches:

* To reduce the size of light textures, use the **Render Scale** property of the [2D Renderer asset](/engine/6000.0/manual/unity2d/2d-urp/2drenderer-data-overview.md).
* If you have a lot of sorting layers that each have their own set of lights, increase the **Max Light Render Textures** in the [2D Renderer asset](/engine/6000.0/manual/unity2d/2d-urp/2drenderer-data-overview.md) so Unity can pre-render all the light textures in one go. This can increase the amount of memory Unity uses.
* To reduce the number of light textures, use fewer different **Blend Style** values in the [2D lights](/engine/6000.0/manual/unity2d/2d-urp/2d-index/2dlight-properties.md) in your scene. Each different blend style you use creates a new light render texture. The best practice is to use only one or two different blend styles in a scene.

## Lighting Batching Debugger window reference


**The Light Batching Debugger window with the batch panel on the left (A), and the main area on the right (B).:**
![](/api/media?file=/engine/6000.0/media/images/light-batching-debugger-3.PNG)

* A: The list of 2D light batches. Each batch represents one light texture. The **Layers** column lists which sorting layers Unity draws using the light texture.
* B: The main area. When you select two batches, this area lists which lights or shadows prevent Unity merging the batches. In the example, **Light A** needs its own light texture because it targets only the **BG** sorting layer rather than both the **BG** and **Default** sorting layers.

## Additional resources

* [2D Renderer asset component reference for URP](/engine/6000.0/manual/unity2d/2d-urp/2drenderer-data-overview.md)