Along with the official reveal of the Android Marshmallow name, Google has also updated the Android SDK to include the new update. This update confirms Android Marshmallow as version 6.0. API 23 is along with this. A third version of the Android M developer preview is also now available. This new preview is the third and final update to the developer preview. After this we’ll get the final release version of Android 6.0.
Via: Android Police