Realme C21Y comes with a 6.50-inch touchscreen display with a resolution of 720×1600 pixels and an aspect ratio of 20:9. Realme C21Y is powered by an octa-core Unisoc T610 processor. It comes with 4GB of RAM. The Realme C21Y runs Android 11 and is powered by a 5000mAh battery. The Realme C21Y supports proprietary fast charging. As far as the cameras are concerned, the Realme C21Y on the rear packs a triple camera setup featuring a 13-megapixel primary camera with an f/2.2 aperture; a 2-megapixel camera with an f/2.4 aperture, and a 2-megapixel camera with an f/2.4 aperture. The rear camera setup has autofocus. It has a single front camera setup for selfies, featuring a 5-megapixel sensor with an f/2.4 aperture. The Realme C21Y runs Realme UI is based on Android 11 and packs 64GB of inbuilt storage that can be expanded via microSD card (up to 256GB) with a dedicated slot. The Realme C21Y is a dual-SIM (GSM and GSM) mobile that accepts Nano-SIM and Nano-SIM cards. The Realme C21Y measures 164.50 x 76.00 x 9.10mm (height x width x thickness) and weighs 200.00 grams. It was launched in Cross Black and Cross Blue colours. Connectivity options on the Realme C21Y include Wi-Fi, GPS, Bluetooth v5.00, Micro-USB, 3G, and 4G. Sensors on the phone include accelerometer, ambient light sensor, compass/ magnetometer, proximity sensor, and fingerprint sensor.