The Sony Xperia Z4 and Z5 are confirmed to be receiving an Android 6.0 Marshmallow update after a Wi-Fi certification was spotted for the mobile operating system upgrade for the Sony-built handset and tablet.

The Wi-Fi certification is shown in the Wi-Fi Alliance website, revealing some Japanese handset models that have been approved for Android 6.0 Marshmallow firmware upgrades. Wi-Fi certification is one of the many steps to getting a smartphone ready for an OS update, which approves a gadget for Wi-Fi interoperability, security and a range of other application-specific protocols.

Android 6.0 Marshmallow is now Wi-Fi certified for the Sony Xperia Z5 on NTT docomo (SO-01H), SoftBank (501SO) and au (SOV32), and NTT docomo Xperia Z5 Premium (SO-03H). The Xperia Z4 tablet on NTT docomo (SO-03G), SoftBank (402SO) and au (SOV31) have also received Wi-Fi certifications.

Android device owners have long been on the lookout for any signs that would confirm the arrival of an OTA update of the Android 6.0 Marshmallow mobile operating system. The firmware update, though not as major as Lollipop, promises a wide variety of new features and upgrades including a new Doze Mode, a smart standby system that is seen to bring improvements to battery life.

Other upgrades include access to Android Pay, enhanced systems for fingerprint scanners, improved user experience designs and many more.

The Xperia Z5 is Sony's latest flagship handset that sports a 5.2-inch IPS LCD capacitive touchscreen with 1080 x 1920 pixel resolution. The smartphone is powered by a Qualcomm MSM8994 Snapdragon 810, and has 3 GB of RAM. DxO Mark gives the Xperia Z5's camera a score of 87, one of the highest mobile photo and video scores to date.

The Xperia Z4 tablet, on the other hand, is Sony's latest tablet release, and sports a 10.1-inch screen with a 2560x1600 pixel display.

The Wi-Fi certification provides no set date as to when the Sony Xperia Z4 and Z5, neither does it imply that the update will be arriving soon, but users can expect to hear more from Sony by the time the new year comes.