The Lumia 950 XL has a polycarbonate frame with a removable back shell, allowing access to the battery as well as SIM and microSD card slots.

[9] The Lumia 950 XL has a 20 MP PureView-branded rear-facing camera, containing a 1/2.4 in BSI sensor with 1.12 μm pixels and phase-detection autofocus, a 6-element Carl Zeiss lens with a f/1.9 aperture and 5th-gen optical image stabilization, and a triple-LED RGB flash that can adjust to match the color of ambient light.

The camera can also capture oversampled 8 MP images, optionally with a full-resolution DNG file that enables more post-processing possibilities.

The latter supports USB OTG, enabling the use of peripherals like mice, flash drives or external microphones,[14] and USB-C fast charging.

[32] The Lumia 950 XL was generally well-received, with most reviewers commending the high-end specifications and camera performance, but finding the design to be less "premium" than competing flagships, and the app ecosystem to be less comprehensive than Android or iOS.

GSMArena gave the Lumia 950 XL a very favorable review, praising the specifications, display and camera, and commending Microsoft's unification of the UI and app stores of Windows 10 on mobile and desktop devices.

[34] Dragan Petric of Notebook Review criticized the ergonomics, saying the phone "doesn’t feel comfortable to hold" due to some sharp edges, and considered the design to be unfitting of a flagship device.

[35] Hannah Francis of The Sydney Morning Herald called the Lumia 950 XL "different, but not in a good way", commending Microsoft for features like Continuum but criticizing the execution.

The Edge browser was highlighted as performing very well, and the reviewer also praised the display and camera, describing images taken with the phone as having "an astonishing level of detail".