Version: 2018.2 (switch to 2018.3b or 2017.4)
Understanding Automatic Memory Management
Special folders and script compilation order
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Platform dependent compilation

Unity includes a feature called Platform Dependent Compilation. This consists of some preprocessor directives that let you partition your scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary
to compile and execute a section of code exclusively for one of the supported platforms.

You can run this code within the Unity Editor, so you can compile the code specifically for your target platform and test it in the Editor!

Platform #define directives

The platform #define directives that Unity supports for your scripts are as follows:

Property: Function:
UNITY_EDITOR #define directive for calling Unity Editor scripts from your game code.
UNITY_EDITOR_WIN #define directive for Editor code on Windows.
UNITY_EDITOR_OSX #define directive for Editor code on Mac OS X.
UNITY_STANDALONE_OSX #define directive for compiling/executing code specifically for Mac OS X (including Universal, PPC and Intel architectures).
UNITY_STANDALONE_WIN #define directive for compiling/executing code specifically for Windows standalone applications.
UNITY_STANDALONE_LINUX #define directive for compiling/executing code specifically for Linux standalone applications.
UNITY_STANDALONE #define directive for compiling/executing code for any standalone platform (Mac OS X, Windows or Linux).
UNITY_WII #define directive for compiling/executing code for the Wii console.
UNITY_IOS #define directive for compiling/executing code for the iOS platform.
UNITY_IPHONE Deprecated. Use UNITY_IOS instead.
UNITY_ANDROID #define directive for the Android platform.
UNITY_PS4 #define directive for running PlayStation 4 code.
UNITY_XBOXONE #define directive for executing Xbox OneMicrosoft’s eighth generation video game console.
See in Glossary
code.
UNITY_TIZEN #define directive for the Tizen platform.
UNITY_TVOS #define directive for the Apple TV platform.
UNITY_WSA #define directive for Universal Windows PlatformAn IAP feature that supports Microsoft’s In App Purchase simulator, which allows you to test IAP purchase flows on devices before publishing your application. More info
See in Glossary
. Additionally, NETFX_CORE is defined when compiling C# files against .NET Core and using .NET scripting backendA framework that powers scripting in Unity. Unity supports three different scripting backends depending on target platform: Mono, .NET and IL2CPP. Universal Windows Platform, however, supports only two: .NET and IL2CPP. More info
See in Glossary
.
UNITY_WSA_10_0 #define directive for Universal Windows Platform. Additionally WINDOWS_UWP is defined when compiling C# files against .NET Core.
UNITY_WINRT Same as UNITY_WSA.
UNITY_WINRT_10_0 Equivalent to UNITY_WSA_10_0
UNITY_WEBGL #define directive for WebGLA JavaScript API that renders 2D and 3D graphics in a web browser. The Unity WebGL build option allows Unity to publish content as JavaScript programs which use HTML5 technologies and the WebGL rendering API to run Unity content in a web browser. More info
See in Glossary
.
UNITY_FACEBOOK #define directive for the Facebook platform (WebGL or Windows standalone).
UNITY_ADS #define directive for calling Unity Ads methods from your game code. Version 5.2 and above.
UNITY_ANALYTICS #define directive for calling Unity AnalyticsA data platform that provides analytics for your Unity game. More info
See in Glossary
methods from your game code. Version 5.2 and above.
UNITY_ASSERTIONS #define directive for assertions control process.

From Unity 2.6.0 onwards, you can compile code selectively. The options available depend on the version of the Editor that you are working on. Given a version number X.Y.Z (for example, 2.6.0), Unity exposes three global #define directives in the following formats: UNITY_X, UNITY_X_Y and UNITY_X_Y_Z.

Here is an example of #define directives exposed in Unity 5.0.1:

UNITY_5 #define directive for the release version of Unity 5, exposed in every 5.X.Y release.
UNITY_5_0 #define directive for the major version of Unity 5.0, exposed in every 5.0.Z release.
UNITY_5_0_1 #define directive for the minor version of Unity 5.0.1.

Starting from Unity 5.3.4, you can compile code selectively based on the earliest version of Unity required to compile or execute a given portion of code. Given the same version format as above (X.Y.Z), Unity exposes one global #define in the format UNITY_X_Y_OR_NEWER, that can be used for this purpose.

The supported #define directives are:

ENABLE_MONO Scripting backend #define for Mono.
ENABLE_IL2CPP Scripting backend #define for IL2CPPA Unity-developed scripting back-end which you can use as an alternative to Mono when building projects for some platforms. More info
See in Glossary
.
ENABLE_DOTNET Scripting backend #define for .NET.
NETFX_CORE Defined when building scripts against .NET Core class libraries on .NET.
NET_2_0 Defined when building scripts against .NET 2.0 API compatibility level on Mono and IL2CPP.
NET_2_0_SUBSET Defined when building scripts against .NET 2.0 Subset API compatibility level on Mono and IL2CPP.
NET_4_6 Defined when building scripts against .NET 4.x API compatibility level on Mono and IL2CPP.
NET_STANDARD_2_0 Defined when building scripts against .NET Standard 2.0 API compatibility level on Mono and IL2CPP.
ENABLE_WINMD_SUPPORT Defined when Windows Runtime support is enabled on IL2CPP and .NET. See Windows Runtime Support for more details.

You use the DEVELOPMENT_BUILD #define to identify whether your script is running in a player which was built with the “Development BuildA development build includes debug symbols and enables the Profiler. More info
See in Glossary
” option enabled.

You can also compile code selectively depending on the scripting back-end.

Testing precompiled code

Below is an example of how to use the precompiled code. It prints a message that depends on the platform you have selected for your target build.

First of all, select the platform you want to test your code against by going to File > Build Settings. This displays the Build Settings window; select your target platform from here.

Build Settings window with PC, Mac & Linux selected as the target platforms
Build Settings window with PC, Mac & Linux selected as the target platforms

Select the platform you want to test your precompiled code against and click Switch Platform to tell Unity which platform you are targeting.

Create a script and copy/paste the following code:

// JS
function Awake() {
  #if UNITY_EDITOR
    Debug.Log("Unity Editor");
  #endif
    
  #if UNITY_IPHONE
    Debug.Log("Iphone");
  #endif

  #if UNITY_STANDALONE_OSX
    Debug.Log("Stand Alone OSX");
  #endif

  #if UNITY_STANDALONE_WIN
    Debug.Log("Stand Alone Windows");
  #endif    
}


// C#
using UnityEngine;
using System.Collections;

public class PlatformDefines : MonoBehaviour {
  void Start () {

    #if UNITY_EDITOR
      Debug.Log("Unity Editor");
    #endif
    
    #if UNITY_IOS
      Debug.Log("Iphone");
    #endif

    #if UNITY_STANDALONE_OSX
    Debug.Log("Stand Alone OSX");
    #endif

    #if UNITY_STANDALONE_WIN
      Debug.Log("Stand Alone Windows");
    #endif

  }          
}


To test the code, click Play Mode. Confirm that the code works by checking for the relevant message in the Unity console, depending on which platform you selected - for example, if you choose iOSApple’s mobile operating system. More info
See in Glossary
, the message “Iphone” is set to appear in the console.

In C# you can use a CONDITIONAL attribute which is a more clean, less error-prone way of stripping out functions. See ConditionalAttribute Class for more information. Note that common Unity callbacks (ex. Start(), Update(), LateUpdate(), FixedUpdate(), Awake()) are not affected by this attribute because they are called directly from the engine and, for performance reasons, it does not take them into account.

In addition to the basic #if compiler directive, you can also use a multiway test in C#:


#if UNITY_EDITOR
    Debug.Log("Unity Editor");

#elif UNITY_IOS
    Debug.Log("Unity iPhone");

#else
    Debug.Log("Any other platform");

#endif


Platform custom #defines

It is also possible to add to the built-in selection of #define directives by supplying your own. Open the Other Settings panel of the Player SettingsA settings manager that lets you set various player-specific options for the final game built by Unity. More info
See in Glossary
and navigate to the Scripting Define Symbols text box.

Enter the names of the symbols you want to define for that particular platform, separated by semicolons. These symbols can then be used as the conditions for #if directives, just like the built-in ones.

Global custom #defines

You can define your own preprocessor directives to control which code gets included when compiling. To do this you must add a text file with the extra directives to the AssetsAny media or data that can be used in your game or project. An asset may come from a file created outside of Unity, such as a 3D model, an audio file or an image. You can also create some asset types in Unity, such as an Animator Controller, an Audio Mixer or a Render Texture. More info
See in Glossary
folder. The name of the file depends on the language you are using. The extension is .rsp:

C# (player and editor scripts) <Project Path>/Assets/mcs.rsp

As an example, if you include the single line -define:UNITY_DEBUG in your mcs.rsp file, the #define directive UNITY_DEBUG exists as a global #define for C# scripts, except for Editor scripts.

Every time you make changes to .rsp files, you need to recompile in order for them to be effective. You can do this by updating or reimporting a single script (.js or .cs) file.

NOTE

If you want to modify only global #define directives, use Scripting Define Symbols in Player Settings, as this covers all the compilers. If you choose the .rsp files instead, you need to provide one file for every compiler Unity uses, and you don’t know when one or another compiler is used.

The use of .rsp files is described in the ‘Help’ section of the mcs application which is included in the Editor installation folder. You can get more information by running mcs -help.

Note that the .rsp file needs to match the compiler being invoked. For example:

  • when targeting any players or the editor, mcs is used with mcs.rsp, and
  • when targeting MS compiler, csc is used with csc.rsp, etc(Ericsson Texture Compression) A block-based texture format that compresses textures to significantly reduce file sizes without causing a noticable reduction in image quality. More info
    See in Glossary
    .

  • 2018–03–16 Page amended with no editorial review

  • Removed Samsung TV support.

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Understanding Automatic Memory Management
Special folders and script compilation order