EditorApplication.isPlaying

Description

Whether the Editor is in Play mode.

Returns true if the Editor is in Play mode. Setting isPlaying delays the result until after all script code has completed for this frame. This also returns true if the Editor is paused.

Additional resources: isPaused, isPlayingOrWillChangePlaymode.

using UnityEngine;
using UnityEditor;

// The following is a simple example where EditorApplication.isPlaying is watched to
// report whether the Editor is in Play mode.

public class EditorPlaying : EditorWindow
{
    [MenuItem("Examples/EditorApplication.isPlaying demo")]
    static void Init()
    {
        EditorWindow window = GetWindow(typeof(EditorPlaying));
        window.position = new Rect(100, 100, 150, 50);
        window.Show();
    }

    void OnGUI()
    {
        if (EditorApplication.isPlaying)
        {
            EditorGUILayout.LabelField("Playing");
        }
        else
        {
            EditorGUILayout.LabelField("Not playing");
        }
    }
}