Import a file from the shader library in the Built-In Render Pipeline

Important: The Built-In Render Pipeline is deprecated and will be made obsolete in a future release.
It remains supported, including bug fixes and maintenance, through the full Unity 6.7 LTS lifecycle.
For more information on migration, refer to Migrating from the Built-In Render Pipeline to the Universal Render Pipeline and Render pipeline feature comparison.

Unity contains several files that can be used by your shader programs to bring in predefined variables and helper functions. This is done by the standard #include directive, e.g.:

SubShader {
    Pass {
        HLSLPROGRAM

        #include "UnityCG.cginc"

        ENDHLSL
    }
}

Shader include files in Unity are with .cginc extension, and the built-in ones are:

HLSLSupport.cginc: Declares various preprocessor macros to aid in multi-platform shader development. Unity automatically includes this file if you use CGPROGRAM. For more information, refer to Shader code blocks in ShaderLab reference.
UnityShaderVariables.cginc: Declares various built-in global variables that are commonly used in shaders. Unity automatically includes this file if you use CGPROGRAM. For more information, refer to Shader code blocks in ShaderLab reference.
UnityCG.cginc: Commonly used built-in helper functions and data structures.
AutoLight.cginc: Lighting and shadowing functionality, for example surface shadersA streamlined way of writing shaders for the Built-in Render Pipeline. More info
See in Glossary use this file internally.
Lighting.cginc: Standard surface shader lighting models. Unity automatically includes this file if your write surface shaders.
TerrainEngine.cginc: Helper functions for terrain and vegetation shaders.

Note: Although shader library files have a .cginc file extension, they’re written in HLSL rather than CG.

These files are found inside Unity application ({unity install path}/Data/Resources/CGIncludes/UnityCG.cginc on Windows, /Applications/Unity/Unity.app/Contents/Resources/CGIncludes/UnityCG.cginc on Mac), if you want to take a look at what exactly is done in any of the helper code.

Shader methods in the Built-In Render Pipeline

Use built-in HLSL structures in the Built-In Render Pipeline

Unity Manual

Import a file from the shader library in the Built-In Render Pipeline