The OnePlus 3 is beginning to see the OxygenOS 4.0.1 update, kicking it forward to a slightly newer version of Android Nougat after having just recently sent out more updates for Android 7.0 in the form of OxygenOS 4.0 back on January 2nd (initially on New Year's Eve), alongside the OnePlus 3T. Since most OnePlus 3 devices are likely already on Android 7.0 Nougat through the software update to OxygenOS 4.0 that OnePlus started rolling out earlier this month, this minor bump in software isn't going to bring along with it a large amount of feature changes and new functionality, in fact the update looks to be mostly the same.
In regards to what's actually new or what's changed with this update, there really doesn't look to be too much, if anything different from the update that started going out on New Year's Eve, as the screenshots for the OxygenOS 4.0.1 update show all of the exact same "what's new" details from the changelog. This includes being updated to Android 7.0 Nougat, which suggests that OxygenOS 4.0.1 is simply a slightly different update version of Nougat for a certain variation of the OnePlus 3 that had not already been updated from Android Marshmallow.
In addition to the Nougat software, the changelog also mentions other details that many users on OxygenOS 4.0 already have, like custom DPI support, Notification Direct Reply, multi-window support, new designs for the settings menu and the notifications, improved shelf customization and more. Even with all of these changes and a bump to Android 7.0, the download file size is only listed at 36MB which isn't very large. Regardless of the file size of the update and that the changes look to be the same as with version 4.0, this does seem to showcase that OnePlus is being ever diligent as always in getting updates out to their devices as quickly as they can, especially so soon after the first of the year and after a recent update to the same device. OnePlus 3 owners that haven't already received the update to OxygenOS 4.0.1 can always check to see if the update is available manually, which can be done by navigating to settings, then to the about phone section, and tapping on software updates.