In versions of Unity prior to v5, plugins were added to a project by placing them in specially-named folders to identify the target platform (OSX, Android, etc). From v5 onwards, plugins can be placed at any convenient place in the project, since the target platforms are now selected from the inspector.
If you select a plugin file (or bundle, etc) in your project, you will see the plugin inspector.
The checkboxes at the top let you choose the platforms which will use the plugin.
The Platforms tab lets you choose the platforms that will use the plugin. If you select Any as the platform then the plugin will apply to all platforms, including the Unity editor. Once you have selected the platforms, you can choose additional options (CPU type, specific OS, etc) from the separate Platform Settings section below. This contains a tab for each platform selected by the checkboxes. Most platforms have no setting or just a few (eg, CPU and OS selection).
Certain folders are treated as a single bundle plugin. No additional plugins are detected within such folders. At this moment the following extensions identify folders that are treated as bundle plugins:
To make transition easier from earlier Unity versions, Unity will try to set default plugins settings, depending on the folder where the plugin is located.
|Assets/**/Editor||Plugin will be set only compatible with Editor, and won’t be used when building to platform.|
|Assets/**/Editor/(x86 or x86_64 or x64)||Plugin will be set only compatible with Editor, CPU value will be assigned depending on the subfolder.|
|Assets/**/Plugins/x86_64(or x64)||x64 Standalone plugins will be set as compatible.|
|Assets/**/Plugins/x86||x86 Standalone plugins will be set as compatible.|
|Assets/Plugins/Android/(x86 or armeabi or armeabi-v7a)||Plugin will be set only compatible with Android, if CPU subfolder is present, CPU value will be set as well.|
|Assets/Plugins/iOS||Plugin will be set only compatible with iOS.|
|Assets/Plugins/WP8/(x86 or ARM)||Plugin will be set only compatible with Windows Phone 8, if subfolder is CPU present, CPU value will be set as well.|
|Assets/Plugins/WSA/(x86 or ARM)||Plugin will be set only compatible with Windows Store Apps and Windows Phone 8.1, if subfolder is CPU present, CPU value will be set as well. Note. Metro keyword can be used instead of WSA.|
|Assets/Plugins/WSA/(SDK80 or SDK81 or PhoneSDK81)||Same as above, additionally SDK value will be set, you can also add CPU subfolder afterwards. For compatibility reasons, SDK80 is the same as Win80, SDK81 - Win81, PhoneSDK81 - WindowsPhone81.|
|Assets/Plugins/Tizen||Plugin will be set only compatible with Tizen.|
|Assets/Plugins/Xbox360||Plugin will be set only compatible with Xbox360.|
|Assets/Plugins/PSVita||Plugin will be set only compatible with Playstation Vita.|
|Assets/Plugins/PS3||Plugin will be set only compatible with Playstation 3.|
|Assets/Plugins/PS4||Plugin will be set only compatible with Playstation 4.|
|Assets/Plugins/SamsungTV||Plugin will be set only compatible with Samsung TV.|
For instance, if you select CPU X86, the plugin will be used only in 32 bit Editor, but will not be used in 64 bit Editor.
If you select OS Windows, the plugin will be used only in Windows Editor, but will not be used by the OS X Editor.