Vivo X21 UD comes with Android 8.0 (Oreo) OS, 6.28 inches Super AMOLED LCD capacitive touchscreen, 16M colors and 1080 x 2280 pixels resolution + 402 PPI pixel density, It has Black, Aurora White, Ruby Red color, Dual SIM (Nano-SIM, dual stand-by) Slot supports 2G, 3G and 4G LTE network.
The smartphone has Dual 12 MP f/1.8 + 5 MP, autofocus rear camera having geo-tagging, touch focus, face detection, HDR and panorama features and 12 MP f/2.0 front camera for selfie experience.
Vivo X21 UD has Octa-core (4x2.2 GHz Kryo 260 & 4x1.8 GHz Kryo 260) processor, Qualcomm SDM660 Snapdragon 660 chipset and Adreno 512 GPU.
It has 6GB RAM and 128GB internal Storage, microSD, up to 256 GB card slot. It brings Bluetooth 5.0, A2DP, LE + microUSB v2.0 and 3.5 mm Audio jack.
Here is 3200mAh battery with fast charging but no wireless charger support.
The smartphone has Fingerprint (under display), accelerometer, proximity and compass sensors.