| Hardware and OS | Karbonn Smart A66 | Oppo A3s |
| Operating system | Android v4.4 (KitKat) | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | 1.2 GHz, Dual Core Processor | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| RAM | 256 MB | |
| GPU | | Adreno 506 |
| Internal memory | 512 MB | 16 GB, 2 GB RAM |
| Memory Card Slot | Yes, upto 32 GB | |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| Dual Sim | Yes | |
| Sim Type | Dual Sim, GSM GSM | |
| Display | Karbonn Smart A66 | Oppo A3s |
| Type | | IPS LCD |
| Size | | 6.2" inc |
| Screen Size | 3.5 inches, 320 x 480 pixels | |
| Resolution | | 720 x 1520 px |
| Display Type | Color LCD screen | |
| Touchscreen | | capacitive touchscreen |
| Screen-to-Body Ratio | | 81.2% |
| Touch Screen | Yes | |
| Display area | | 95.9 cm2 |
| Display aspect ratio | 3:2 | 19:9 (height:width) |
| Pixel Density | ~165 PPI | 271 PPI |
| Colors | | 16M |
| Connectivity | Karbonn Smart A66 | Oppo A3s |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| 3G Network | No | HSDPA 850 / 900 / 2100 |
| 4G Network | | LTE |
| Wi-Fi | | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| Wifi | Yes, with wifi-hotspot | |
| Network | | GSM / HSPA / LTE |
| SIM card | | Dual SIM (Nano-SIM, dual stand-by) |
| Bluetooth | Yes | 4.2, A2DP, LE |
| Edge | Yes | Yes |
| GPRS | Yes | Yes |
| GPS | No | Yes, with A-GPS |
| Speed | | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | Yes | microUSB 2.0, USB On-The-Go |
| Camera | Karbonn Smart A66 | Oppo A3s |
| Flash | Yes, LED | |
| Main camera | 3 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 | 0.3 MP | 8 MP, Single |
| Multimedia | Karbonn Smart A66 | Oppo A3s |
| FM Radio | No | |
| Java | Yes, via 3rd party | |
| 3.5 mm Jack | | Yes |
| Radio | | FM radio |
| Design | Karbonn Smart A66 | Oppo A3s |
| Colors | | Red, Dark Purple |
| Dimensions | | 156.2 x 75.6 x 8.2 mm |
| Weight | | 168 g |
| Battery | Karbonn Smart A66 | Oppo A3s |
| Type | Removable Battery | |
| Battery capacity | 1100 mAh, Li-ion Battery | 4230 mAh, Non-removable Li-Ion |
| Other | Karbonn Smart A66 | Oppo A3s |
| Release date | | 2018, July |
| Sensors | | Accelerometer, proximity, compass |
