Set preprocessor symbols from Editor script

I’m working on a very simple build utility and I want to programmatically add/remove preprocessor symbols before builds.

For example, if I have Build Android-Release button, I want to programmatically add a RELEASE preprocessor to the build settings before I start the build. Or if I wanted to make a device-specific build for OUYA, I could add an appropriate symbol instead of managing that manually in the Editor.

I have found EditorUserBuildSettings.activeScriptCompilationDefines but is read-only. Any suggestions?


Set your preprocessor definitions in: Player Settings → Per-platform Settings → Other Settings → Configuration → Scripting Define Symbols.

EDIT: If you have multiple definitions, separate with a semicolon.

EDIT: From an editor script, use PlayerSettings.SetScriptingDefineSymbolsForGroup to set these same values programmatically, which is what I would have said if I had exercised the slightest bit of reading comprehension the first time. (apologies)

You can use AddDefineSymbols to add define symbols automatically.


  • Multiple Define Symbols
  • Safety
  • Runs when Compile ends
  • Removes Duplicates


  1. Download the Script or Copy/Paste it from the Below
  2. Open Script
  3. Go to Symbols property and add your own symbols
  4. Go back to Unity and wait for compile ends
  5. All done, now check Player Settings, The symbols added

Here is the code for copy/pasting:

using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using UnityEditor;
/// <summary>
/// Adds the given define symbols to PlayerSettings define symbols.
/// Just add your own define symbols to the Symbols property at the below.
/// </summary>
public class AddDefineSymbols : Editor
    /// <summary>
    /// Symbols that will be added to the editor
    /// </summary>
    public static readonly string [] Symbols = new string[] {
    /// <summary>
    /// Add define symbols as soon as Unity gets done compiling.
    /// </summary>
    static AddDefineSymbols ()
        string definesString = PlayerSettings.GetScriptingDefineSymbolsForGroup ( EditorUserBuildSettings.selectedBuildTargetGroup );
        List<string> allDefines = definesString.Split ( ';' ).ToList ();
        allDefines.AddRange ( Symbols.Except ( allDefines ) );
        PlayerSettings.SetScriptingDefineSymbolsForGroup (
            string.Join ( ";", allDefines.ToArray () ) );