| Hardware and OS | Realme C21Y | |
| Operating system | Android 10, Realme UI | |
| Processor | Octa-core (2x1.8 GHz Cortex-A75 & 6x1.8 GHz Cortex-A55) | |
| Chipset | Unisoc T610 (12 nm) | |
| Internal memory | 32GB 3GB RAM, 64GB 4GB RAM | |
| External memory | microSDXC (dedicated slot) | |
| GPU | Mali-G52 | |
| Display | Realme C21Y | other phones |
| Size | 6.5 inches, 102.0 cm2 | |
| Resolution | 720 x 1600 pixels, 20:9 ratio | |
| Type | IPS LCD, 400 nits (typ) | |
| Main Camera | Realme C21Y | other phones |
| Camera | 13 MP, f/2.2, 26mm (wide), 1/3.06", 1.12µm, PDAF
2 MP, f/2.4, (macro)
2 MP, f/2.4, (depth) | |
| Features | LED flash, HDR, panorama | |
| Video | 1080p@30fps | |
| Selfie camera | Realme C21Y | other phones |
| Camera | 5 MP, f/2.2, (wide), 1/5.0", 1.12µm | |
| Features | HDR, panorama | |
| Video | 1080p@30fps | |
| Connectivity | Realme C21Y | other phones |
| 2G Network | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 | |
| 3G Network | HSDPA 850 / 900 / 2100 | |
| 4G Network | 1, 3, 5, 8, 38, 40, 41 | |
| Bluetooth | 5.0, A2DP, LE | |
| GPS | Yes, with A-GPS, GLONASS, BDS | |
| NFC | No | |
| Speed | HSPA 42.2/5.76 Mbps, LTE | |
| Technology | GSM / HSPA / LTE | |
| USB | microUSB 2.0, USB On-The-Go | |
| WLAN | Wi-Fi 802.11 b/g/n, hotspot | |
| Multimedia | Realme C21Y | other phones |
| 3.5 mm Jack | Yes | |
| Loudspeaker | Yes | |
| Radio | Unspecified | |
| Battery | Realme C21Y | other phones |
| Type | Li-Po 5000 mAh, non-removable | |
| Charging | Reverse charging | |
| Design | Realme C21Y | other phones |
| Body build | Glass front, plastic back, plastic frame | |
| Colors | Cross Black, Cross Blue | |
| Dimensions | 164.5 x 76 x 9.1 mm (6.48 x 2.99 x 0.36 in) | |
| Weight | 200 g (7.05 oz) | |
| SIM | Dual SIM (Nano-SIM, dual stand-by) | |
| Features | Realme C21Y | other phones |
| Sensors | Fingerprint (rear-mounted), accelerometer, proximity, compass | |
