Debug.isDebugBuild Manual     Reference     Scripting  
Scripting > Runtime Classes > Debug

static var isDebugBuild : bool


In the Build Settings ... dialog there is a check box called "strip debug symbols".

If it is checked isDebugBuild will be off. In the editor isDebugBuild always returns true. It is recommended to remove all calls to Debug.Log when deploying a game, this way you can easily deploy beta builds with debug prints and final builds without.

// Log some debug information only if this is a debug build
if (Debug.isDebugBuild) {
Debug.Log ("Something bad happened!");