After rolling out the Android 6 Marshmallow update to USA users, HTC has started pushing the update to Asian HTC One M8 units. The update is rolled out via Over-The-Air(OTA) update.
The Android 6 Marshmallow update is rolling out to only Asian countries. But Indian One M8 users are not getting the update. The company might release the update to Indian users soon.
The build number of the Android 6 Marshmallow update is 6.14.707.1. The build is number is different then the one seeded to unlocked HTC One M8 users in US.
It indicates that HTC has fixed many bugs while pushing the update to non-India Asian HTC One M8 users. The update is of size 1.14GB, so it is advisable to download the update via Wi-Fi network.
Android 6 Marshmallow update brings several new features to HTC One M8 like App Permissions, Doze Mode, Now on Tap and other critical security fixes.