Blog Posts Surface Duo

A technical look inside the Microsoft Surface Duo

Surface Duo is here, the reviews are out, and people have finally gotten their hands on Microsoft’s first dual-screen device. While the reception to the software was mixed as some bugs have yet to be ironed out, the hardware was heavily praised.

To better understand just how much effort and attention to detail went into building the hardware of Surface Duo, here’s a technical look inside the device and everything that makes it feel so premium in the hand.

Microsoft has been reluctant to call the Duo a “phone”, instead referring to it a member of the Surface family that happens to make phone calls and fit in your pocket.


That last part was extremely important to the engineering team. Ensuring that the device was thin and comfortable enough to fit in people’s pockets.

Surface Duo is only 4.8mm thin when unfolded. Removing the display and back cover glass leaves only 3.7mm of space for the internal components. If that wasn’t a challenge enough on its own, Microsoft also had to make sure that the device lived up to the Surface name in build quality.


Microsoft used premium materials both internally and externally on the Surface Duo. Gorilla Glass 5 was used on both sides of the device, stainless steel on the hinge, and a composite aluminum frame to hold everything in this 250g package together.


Surface Duo features two identical displays. Each are 5.6 inch AMOLEDs with a resolution of 1800×1350, bringing the PPI to about 401. They also go up to 600 nits of brightness. The displays have an aspect ratio of 3:4, with plenty of horizontal real estate for apps to utilize.


The hinge was one of the most praised aspects of the Surface Duo when it landed in the hands of reviewers. Microsoft made it so that it was seamless to fold and unfold, yet solid enough to not flail about.

Similar to other Surface devices like the Surface Pro and Surface Book, Surface Duo features a full friction hinge. 4 custom micro-gears with offset idlers enable 360 degree rotation of the displays. Running between them is 56 bundled micro-coax cables that transfer power and data between the halves, with each strand thinner than a human hair.

Microsoft opted to use two accelerometers, one in each half of the device to detect the angle of the hinge and convey that data to the operating system when using Duo in different postures.

Internal Components

In order to achieve a balanced center of gravity, Microsoft had to be careful in how it distributed the internal components, while also keeping thermals in mind.

The device features a Snapdragon 855 built on a 7nm manufacturing process, 6GB of LPDDR4X RAM, 128 or 256 GB of UFS 3.0 storage, Bluetooth 5.0, Wi-Fi 5, 4G LTE Advanced, NanoSIM and eSIM support, and an 11MP f/2.0 camera that supports up to 4K video recording at 60 fps.

Dual microphones support noise cancellation to make your voice sound clearer in phone and conference calls. There’s one on each display to ensure that your voice is picked up whether both screens are being used or when one is screen is folded back.


Surface Duo features two batteries, one under each display. Under the left display is a 10.37 Wh unit while the one under the right display is rated at 2.89 Wh, bringing the total to 13.26 Wh. Microsoft designed the circuitry in a way that allows the batteries to individually power components on either half of the device.

According to Microsoft, the combined 3577 mAh batteries can be “fast charged” over USB-C 3.1 using the included 18W power supply.

Pen & Inking

Surface Duo supports pen input using the Surface Pen. It can be used to navigate around the UI or for inking/drawing purposes in apps that support it.

Microsoft uses a propriety G5 controller and a “machine learning pen tip algorithm” to enable additional capabilities like pen hover actions, allowing apps to detect the pen when it is hovering just over the display and present certain interactions. An example of this would be showing quick actions to delete, archive, or reply to an email in the Outlook app.

Operating System

Designed with productivity in mind, Surface Duo is the first Microsoft device to run Android. This was a conscious choice, made to ensure users have access to all of the apps they need on a day-to-day basis. Android 10 comes pre-installed, and an upgrade to Android 11 is expected soon.

While Surface Duo can run any Android app in single-screen mode, some apps have been specifically optimized for the device. These apps are aware of the hinge between the displays and can shift their UI elements around it. Microsoft calls this spanning, and while every app can be spanned, ignoring the hinge, optimized apps won’t place buttons or other UI elements beneath the hinge, making them difficult or impossible to reach.

Microsoft has confirmed that Surface Duo’s bootloader can be unlocked, potentially paving the way for custom ROMs to be made available for the device.


Security has always been important to Microsoft, and it’s no different in Surface Duo. The foldable features an enterprise-grade biometric fingerprint sensor on the right side of the unit, Microsoft UEFI 4.1.0 firmware, dm-crypt disk encryption, system updates from Microsoft in addition to the Android security updates from Google, built-in information rights management, and SSL 3.0 for data and network transmission.

Looking at all this, it’s clear that Microsoft paid a lot of attention to details while designing and building the Surface Duo, delivering on its promise to boost productivity while mobile.

Sure, there are areas to improve upon. I would personally like to see smaller bezels, and more RAM in particular, given the focus on multitasking, but Surface Duo is a good stepping stone to build upon for future generations of the product.

If you’re lucky enough to have gotten a Surface Duo, I’d love to hear your thoughts on the product. Be sure to also check out the getting started guides and how-tos to learn more about the device.

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