System Requirements for Unity Authoring
* Windows: XP SP2 or later; Mac OS X: Intel CPU & "Leopard" 10.5 or later. Note that Unity was not tested on server versions of Windows and OS X.
* Graphics card with DirectX 9 level (shader model 2.0) capabilities. Any card made since 2004 should work.
* Using Occlusion Culling requires GPU with Occlusion Query support (some Intel GPUs do not support that).
* The rest only depends on the complexity of your projects!.

System Requirements for Unity iOS Authoring
* An Intel-based Mac
* Mac OS X "Snow Leopard" 10.6 or later
* The rest only depends on the complexity of your projects!

System Requirements for Unity Android Authoring
* In addition to the general system requirements for Unity Authoring
* Windows XP SP2 or later; Mac OS 10.5.8 or later
* Android SDK and Java Development Kit (JDK)
* Android authored content requires devices equipped with:
- Android OS 2.0 or later
- Device powered by an ARMv7 (Cortex family) CPU
- GPU support for OpenGLES 2.0 is recommended

System Requirements for Unity-Authored Content
* Windows XP or later; Mac OS X 10.5 or later
* Pretty much any 3D graphics card, depending on complexity.
* Online games run on all browsers, including IE, Firefox, Safari, and Chrome, among others.