| Hardware and OS | Samsung Galaxy M21 2021 | Oppo A3s |
| Operating system | Android 11, One UI 3.1 Core | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | Octa-core (4x2.3 GHz Cortex-A73, 4x1.7 GHz Cortex-A53) | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | Mali-G72 MP3 | Adreno 506 |
| RAM | 4 GB, 6 GB | |
| Internal memory | | 16 GB, 2 GB RAM |
| Internal Storage | 64 GB, 128 GB | |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| Memory Card Slot | microSDXC (dedicated slot) | |
| User Interface | Yes | |
| Display | Samsung Galaxy M21 2021 | Oppo A3s |
| Type | Super AMOLED | IPS LCD |
| Size | 6.4 inches | 6.2" inc |
| Resolution | 1080 x 2340 pixels | 720 x 1520 px |
| Touchscreen | Capacitive touchscreen | capacitive touchscreen |
| Screen-to-Body Ratio | | 81.2% |
| Display area | | 95.9 cm2 |
| Display aspect ratio | | 19:9 (height:width) |
| Pixel Density | 403 PPI | 271 PPI |
| Protection | Corning Gorilla Glass 3 | |
| Colors | 16M | 16M |
| Connectivity | Samsung Galaxy M21 2021 | Oppo A3s |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| 5G Network | No | |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| 4G Network | LTE | LTE |
| Wi-Fi | Wi-Fi 802.11 a/b/g/n/ac, dual-band, Wi-Fi Direct, hotspot | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| NFC | No | |
| Network | | GSM / HSPA / LTE |
| SIM card | | Dual SIM (Nano-SIM, dual stand-by) |
| Bluetooth | | 4.2, A2DP, LE |
| SIM | Nano SIM | |
| Edge | | Yes |
| Dual SIM | Dual SIM (Nano-SIM, dual stand-by) | |
| Wireless Charging | No | |
| GPRS | | Yes |
| GPS | Yes, with A-GPS, GLONASS, GALILEO, BDS | Yes, with A-GPS |
| Speed | HSPA 42.2/5.76 Mbps, LTE-A | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | USB Type-C 2.0 | microUSB 2.0, USB On-The-Go |
| Camera | Samsung Galaxy M21 2021 | Oppo A3s |
| Image | 2160p | |
| Main camera | 48 MP (wide), 8 MP (ultrawide), 5 MP (depth) | 13 MP, Dual |
| Specs | | 13 MP, f/2.2, AF
-2 MP, f/2.4, depth sensor |
| Features | LED flash, panorama, HDR | LED flash, HDR, panorama |
| Video | | 1080p@30fps |
| Selfie camera | 20 MP (wide) | 8 MP, Single |
| Multimedia | Samsung Galaxy M21 2021 | Oppo A3s |
| Loudspeaker | Yes | |
| Handsfree | Yes | |
| Video Playback | Yes | |
| Video Out | Yes | |
| 3.5 mm Jack | Yes | Yes |
| Ring Tones | Yes | |
| Radio | FM radio, RDS, recording | FM radio |
| Design | Samsung Galaxy M21 2021 | Oppo A3s |
| Colors | | Red, Dark Purple |
| Waterproof | No | |
| Dimensions | | 156.2 x 75.6 x 8.2 mm |
| Weight | | 168 g |
| Battery | Samsung Galaxy M21 2021 | Oppo A3s |
| Capacity | Li-Po 6000 mAh, Fast charging 15W | |
| Placement | Non-removable | |
| Battery capacity | | 4230 mAh, Non-removable Li-Ion |
| Other | Samsung Galaxy M21 2021 | Oppo A3s |
| Release date | | 2018, July |
| Sensors | Fingerprint (rear-mounted), accelerometer, gyro, proximity, compass, | Accelerometer, proximity, compass |
