| Hardware and OS | Realme Narzo 21A | Oppo A3s |
| Operating system | Android v10 (Q) | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | Octa-core (4x2.0 GHz Kryo 260 Gold & 4x1.8 GHz Kryo 260 Silver) | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | Qualcomm SDM665 Snapdragon 665 (11 nm) | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | Adreno 610 | Adreno 506 |
| Internal memory | | 16 GB, 2 GB RAM |
| Internal Storage | 64 GB | |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| RAM | 4 GB | |
| Display | Realme Narzo 21A | Oppo A3s |
| Type | | IPS LCD |
| Size | | 6.2" inc |
| Resolution | | 720 x 1520 px |
| Touchscreen | | capacitive touchscreen |
| Screen-to-Body Ratio | | 81.2% |
| Display area | | 95.9 cm2 |
| Display aspect ratio | | 19:9 (height:width) |
| Pixel Density | | 271 PPI |
| Colors | | 16M |
| Connectivity | Realme Narzo 21A | Oppo A3s |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| SIM size | SIM1: Nano, SIM2: Nano | |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| Dual SIM | Dual SIM, GSM GSM | |
| 4G Network | | LTE |
| Wi-Fi | Yes, Wi-Fi 802.11, b/g/n | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| Network support | 4G , 3G, 2G | |
| Network | | GSM / HSPA / LTE |
| USB connectivity | Mass storage device, USB charging | |
| SIM card | | Dual SIM (Nano-SIM, dual stand-by) |
| Bluetooth | Yes, v5.0 | 4.2, A2DP, LE |
| Edge | | Yes |
| GPRS | | Yes |
| GPS | with A-GPS | Yes, with A-GPS |
| Speed | | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | | microUSB 2.0, USB On-The-Go |
| Camera | Realme Narzo 21A | Oppo A3s |
| Autofocus | Yes | |
| Camera features | Digital Zoom, Auto Flash, Face detection, Touch to focus | |
| Flash | Yes, LED Flash | |
| Front camera | 8 MP | |
| Front camera resolution | 8 MP Primary Camera | |
| Video recording | Yes | |
| Main camera | 12 MP 2 MP 2 MP | 13 MP, Dual |
| Specs | | 13 MP, f/2.2, AF
-2 MP, f/2.4, depth sensor |
| Features | | LED flash, HDR, panorama |
| Video | | 1080p@30fps |
| Selfie camera | | 8 MP, Single |
| Multimedia | Realme Narzo 21A | Oppo A3s |
| Audio jack | 3.5 MM | |
| Loudspeaker | Yes | |
| 3.5 mm Jack | | Yes |
| Radio | | FM radio |
| Features | Realme Narzo 21A | Oppo A3s |
| Fingerprint sensor position | Rear | |
| Fingerprint sensor | Yes | |
| Other sensors | Accelerometer, Proximity, Compass | |
| Design | Realme Narzo 21A | Oppo A3s |
| Height | 164.4 mm | |
| Width | 75.4 mm | |
| Thickness | 8.9 mm | |
| Colors | Glory Silver, Victory Blue | Red, Dark Purple |
| Dimensions | | 156.2 x 75.6 x 8.2 mm |
| Weight | 195 grams | 168 g |
| Battery | Realme Narzo 21A | Oppo A3s |
| Capacity | 5000 mAh | |
| Type | Lithium-ion Polymer | |
| User replaceable | No | |
| Battery capacity | | 4230 mAh, Non-removable Li-Ion |
| Other | Realme Narzo 21A | Oppo A3s |
| Release date | | 2018, July |
| Sensors | | Accelerometer, proximity, compass |
