| Hardware and OS | Itel S21 | Oppo A3s |
| Operating system | Android v7.0 (Nougat) | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | Quad core, 1.1 GHz, Cortex A7 | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | MediaTek MT6580M | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | | Adreno 506 |
| Architecture | 32 bit | |
| Internal memory | 16 GB | 16 GB, 2 GB RAM |
| RAM | 1 GB | |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| Expandable Memory | yes Up to 32 GB | |
| Graphics | Mali-400 MP2 | |
| SIM Slot(s) | Dual SIM, GSM GSM | |
| Display | Itel S21 | Oppo A3s |
| Type | | IPS LCD |
| Size | | 6.2" inc |
| Resolution | | 720 x 1520 px |
| Touchscreen | | capacitive touchscreen |
| Screen Size | 5 inches (12.7 cm) | |
| Screen-to-Body Ratio | | 81.2% |
| Screen Resolution | 480 x 854 pixels | |
| Display area | | 95.9 cm2 |
| Display Type | TFT | |
| Display aspect ratio | | 19:9 (height:width) |
| Pixel Density | 196 ppi | 271 PPI |
| Touch Screen | yes Capacitive Touchscreen, Multi-touch | |
| Colors | | 16M |
| Main Camera | Itel S21 | Oppo A3s |
| Resolution | 8 MP Primary Camera
| |
| Image Resolution | 3264 x 2448 Pixels | |
| Flash | yes Dual LED Flash | |
| Camera Features | Digital Zoom, Auto Flash, Face detection, Touch to focus | |
| Autofocus | yes | |
| Shooting Modes | Continuos Shooting, High Dynamic Range mode (HDR) | |
| Settings | Exposure compensation, ISO control | |
| Connectivity | Itel S21 | Oppo A3s |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| 4G Network | | LTE |
| Wi-Fi | yes Wi-Fi 802.11, b/g/n | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| Network | 4G: Available ,
3G: Available, 2G: Available | GSM / HSPA / LTE |
| SIM card | | Dual SIM (Nano-SIM, dual stand-by) |
| Bluetooth | yes v4.1 | 4.2, A2DP, LE |
| Edge | | Yes |
| GPRS | | Yes |
| GPS | yes | 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 |
| SIM 2 | 2G Bands: GSM 1800 / 1900 / 850 / 900 MHz
| |
| NFC | No | |
| VoLTE | yes | |
| Wi-Fi Features | Mobile Hotspot | |
| USB Connectivity | microUSB 2.0 | |
| Front Camera | Itel S21 | Oppo A3s |
| Resolution | 5 MP Primary Camera
| |
| Flash | yes LED Flash | |
| Camera Features | Wide Angle Selfie | |
| Camera | Itel S21 | Oppo A3s |
| Main camera | | 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 | Itel S21 | Oppo A3s |
| 3.5 mm Jack | | Yes |
| Radio | | FM radio |
| Audio Jack | 3.5 mm | |
| FM Radio | yes | |
| Loudspeaker | yes | |
| Design | Itel S21 | Oppo A3s |
| Colors | | Red, Dark Purple |
| Dimensions | | 156.2 x 75.6 x 8.2 mm |
| Weight | | 168 g |
| Colours | Moonlight Silver, Champagne Gold, Elegant Black | |
| Battery | Itel S21 | Oppo A3s |
| Battery capacity | | 4230 mAh, Non-removable Li-Ion |
| Type | Li-Polymer | |
| Capacity | 2700 mAh | |
| USB Type-C | No | |
| Other | Itel S21 | Oppo A3s |
| Release date | | 2018, July |
| Sensors | | Accelerometer, proximity, compass |
| Features | Itel S21 | Oppo A3s |
| Fingerprint Sensor | yes | |
| Fingerprint Sensor Position | Rear | |
