| Hardware and OS | Vivo Y51 | Oppo A3s |
| Operating system | | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | | Adreno 506 |
| Internal memory | | 16 GB, 2 GB RAM |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| Hardware and OS (2020, December) | Vivo Y51 | Oppo A3s |
| Operating system | Android 11, Funtouch 11 | |
| Processor | Octa-core (4x2.0 GHz Kryo 260 Gold, 4x1.8 GHz Kryo 260 Silver) | |
| GPU | Adreno 610 | |
| RAM | 8 GB | |
| Internal Storage | 128 GB | |
| Memory Card Slot | microSDXC (dedicated slot) | |
| User Interface | Yes | |
| Display | Vivo Y51 | 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 |
| Display (2020, December) | Vivo Y51 | Oppo A3s |
| Type | IPS LCD | |
| Size | 6.58 inches | |
| Resolution | 1080 x 2408 pixels | |
| Colors | 16M | |
| Pixel Density | 415 ppi | |
| Touchscreen | Yes | |
| Connectivity (2020, December) | Vivo Y51 | Oppo A3s |
| 4G Network | 1, 3, 5, 8, 40 | |
| 5G Network | No | |
| Wi-Fi | Wi-Fi 802.11 a/b/g/n/ac, dual-band, Wi-Fi Direct, hotspot | |
| GPS | Yes, with A-GPS, GLONASS, GALILEO, BDS | |
| NFC | No | |
| USB | USB Type-C 2.0, USB On-The-Go | |
| Speed | HSPA 42.2/5.76 Mbps, LTE-A | |
| SIM | Nano SIM | |
| Dual SIM | Dual SIM (Nano-SIM, dual stand-by) | |
| Wireless Charging | No | |
| Connectivity | Vivo Y51 | Oppo A3s |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| 4G Network | | LTE |
| Wi-Fi | | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| Network | | GSM / HSPA / LTE |
| SIM card | | Dual SIM (Nano-SIM, dual stand-by) |
| Bluetooth | | 4.2, A2DP, LE |
| Edge | | Yes |
| GPRS | | Yes |
| 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 (2020, December) | Vivo Y51 | Oppo A3s |
| Main camera | 48 MP (wide), 8 MP (ultrawide), 2 MP (macro) | |
| Features | LED flash, HDR, panorama | |
| Image | 1080p | |
| Selfie camera | 16 MP (wide) | |
| Camera | Vivo Y51 | 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 (2020, December) | Vivo Y51 | Oppo A3s |
| Loudspeaker | Yes | |
| Handsfree | Yes | |
| Radio | Yes | |
| Video Playback | Yes | |
| Video Out | Yes | |
| Ring Tones | Yes | |
| 3.5 mm Jack | Yes | |
| Multimedia | Vivo Y51 | Oppo A3s |
| 3.5 mm Jack | | Yes |
| Radio | | FM radio |
| Design (2020, December) | Vivo Y51 | Oppo A3s |
| Dimensions | 163.9 x 75.3 x 8.4 mm | |
| Waterproof | No | |
| Weight | 188 g | |
| Design | Vivo Y51 | Oppo A3s |
| Colors | | Red, Dark Purple |
| Dimensions | | 156.2 x 75.6 x 8.2 mm |
| Weight | | 168 g |
| Battery (2020, December) | Vivo Y51 | Oppo A3s |
| Capacity | Li-Po 5000 mAh, Fast charging 18W, 70% in 67 min (advertised) | |
| Placement | Non-removable | |
| Battery | Vivo Y51 | Oppo A3s |
| Battery capacity | | 4230 mAh, Non-removable Li-Ion |
| Other | Vivo Y51 | Oppo A3s |
| Release date | | 2018, July |
| Sensors | | Accelerometer, proximity, compass |
| Other (2020, December) | Vivo Y51 | Oppo A3s |
| Sensors | Fingerprint (side-mounted), accelerometer, gyro, proximity, compass, | |
