Reduce shader variants in URP

The shadersA program that runs on the GPU. More info
See in Glossary in the Universal Render PipelineA series of operations that take the contents of a Scene, and displays them on a screen. Unity lets you choose from pre-built render pipelines, or write your own. More info
See in Glossary (URP) use shader keywords to support many different features, which can mean Unity compiles a lot of shader variantsA verion of a shader program that Unity generates according to a specific combination of shader keywords and their status. A Shader object can contain multiple shader variants. More info
See in Glossary.

If you disable features in the URP Asset, URP automatically excludes (‘strips’) the related shader variants. This speeds up builds, and reduces memory usage and file sizes.

For example, if your project doesn’t use shadows for directional lights, by default Unity still includes variants that support directional light shadows in your build. If you disable Cast Shadows in the URP Asset, URP strips these variants.

If you want to examine the code that strips shaders in URP, check the Editor/ShaderPreprocessor.cs file. The file uses the IPreprocessShaders API.

For more information on stripping shader variants, refer to the following pages:

• Check how many shader variants you have.
• General guidance on shader stripping, which applies to all render pipelines.

Check how many shader variants your build has

To log how many variants Unity compiles and strips in total, follow these steps:

1. Open the Graphics settings window.
2. In the Shader Stripping section, select a logging level other than Disabled.
3. Build your project.
4. To see the logged information, open the Editor.log log file and search for ShaderStrippingReport. For the location of Editor.log, refer to log files.

To log more detailed shader variant information, follow these steps:

1. Open the Graphics settings window.
2. In the Additional Shader Stripping Settings section, select Export Shader Variants.
3. Build your project.
4. In the folder with your project files, open Temp/graphics-settings-stripping.json and Temp/shader-stripping.json.

For more information, refer to the following in the Unity User Manual:

• Check how many shader variants you have
• Shader variant stripping

Strip feature shader variants

By default, URP compiles variants where a feature is enabled, and variants where a feature is disabled.

To reduce the number of variants, you can enable Strip Unused Variants in URP Graphics settings and do the following:

• Disable a feature in all URP Assets in your build, so URP keeps only variants where the feature is disabled.
• Enable a feature in all URP Assets in your build, so URP keeps only variants where the feature is enabled.

If you disable the Strip Unused Variants setting, URP can’t strip variants where the feature is disabled. This might increase the number of variants.

Disable a feature

To let Unity strip variants related to a feature, make sure you disable it in all the URP Assets in your build.

Unity includes the following URP Assets in your build:

• The URP Asset you set as the default render pipeline asset in Graphics settings.
• Any URP Asset you set as a Render Pipeline Asset in a Quality settings level you enable for the current build target.

Avoid including URP Assets in your build that use different rendering pathsThe technique that a render pipeline uses to render graphics. Choosing a different rendering path affects how lighting and shading are calculated. Some rendering paths are more suited to different platforms and hardware than others. More info
See in Glossary because this causes Unity to create two sets of variants for each keyword.

Strip post-processing shader variants

Enable Strip Unused Post Processing Variants in URP Graphics settings to strip shader variants for Volume Overrides you don’t use.

For example if your project uses only the Bloom effect, URP keeps Bloom variants but strips all other post-processing variants.

Unity checks for Volume Overrides in all scenes, so you can’t strip variants by removing a sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary from your build but keeping it in your project.

You should also enable Strip Screen Coord Override Variants in URP Graphics settings, unless you override screen coordinates to support post processing on large numbers of multiple displays (‘cluster’ displays).

Strip XR and VR shader variants

If you don’t use XRAn umbrella term encompassing Virtual Reality (VR), Augmented Reality (AR) and Mixed Reality (MR) applications. Devices supporting these forms of interactive applications can be referred to as XR devices. More info
See in Glossary or VRVirtual Reality More info
See in Glossary, you can disable the XR and VR modules. This allows URP to strip XR and VR related shader variants from its standard shaders.

Remove variants if you use a custom Renderer Feature

If you create a custom Renderer Feature, you can use the FilterAttribute API to remove shader variants when you enable or disable settings in the URP Asset.

For example, you can do the following:

1. Use [[SerializeField]](https://docs.unity3d.com/ScriptReference/SerializeField.html) to add a Boolean variable to the custom Renderer Feature and add it as a checkbox in the URP Asset InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
   See in Glossary.
2. Use ShaderKeywordFilter.RemoveIf to remove shader variants when you enable the checkbox.

Additional resources

• Troubleshooting shaders