Google’s recently launched flagship Nexus devices (the 6P and 5X) had this useful feature to launch camera quickly, straight from the lockscreen by simply pressing the Power button twice.
Now luckily for the previous generation Nexus devices which received the Android 6.0 Marshmallow update officially, this Double Tap Power Button to launch Camera feature has also been introduced to Nexus 5, 6, 7 (2013) and 9 with the Android 6.0.1 update.
Android 6.0.1 is the first update to Marshmallow release, and is coming after 2 months of the launch of Android 6.0. Apart from the new feature to launch Camera quickly, the update also brings new emojis and bugfixes to Marshmallow running devices.
The double tap power button to launch camera feature should be enabled by default on Android 6.0.1, however, just in case it isn’t, you can enable it by going to Settings » Display » and turn on the “Press power button twice for camera” toggle.
FYI: Nexus 5 is known to have a weak power button, and pressing it twice for camera might not be a good idea. Though we should let you know this.
Note: If it annoys you to get straight to lock screen when exiting the Camera (launched with double tap), you may want to disable the “Power button instantly locks” toggle from Security settings to avoid it.