| Hardware and OS | Karbonn X21 | Oppo A3s |
| Operating system | Android v10 | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | 1.6 GHz, Octa Core Processor | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | Unisoc SC9863 | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | | Adreno 506 |
| RAM | 2 GB | |
| Internal memory | 32 GB | 16 GB, 2 GB RAM |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| Memory Card Slot | Yes, upto 256 GB | |
| Dual Sim | Yes | |
| Sim Size | Nano Nano SIM | |
| Sim Type | Dual Sim, GSM GSM | |
| Display | Karbonn X21 | Oppo A3s |
| Type | | IPS LCD |
| Size | | 6.2" inc |
| Resolution | | 720 x 1520 px |
| Touchscreen | | capacitive touchscreen |
| Screen Size | 5.45 inches, 1440 x 720 pixels | |
| Screen-to-Body Ratio | | 81.2% |
| Display Type | Color HD FullView Display | |
| Display area | | 95.9 cm2 |
| Display aspect ratio | 18:9 | 19:9 (height:width) |
| Touch Screen | Yes, with Multitouch | |
| Pixel Density | ~295 PPI | 271 PPI |
| Colors | | 16M |
| Connectivity | Karbonn X21 | Oppo A3s |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| 3G Network | Yes | HSDPA 850 / 900 / 2100 |
| 4G Network | Yes | 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 | Yes, v4.2 | 4.2, A2DP, LE |
| USB Features | USB on-the-go, USB Charging | |
| Edge | Yes | Yes |
| VoLTE | Yes | |
| GPRS | Yes | Yes |
| Wifi | Yes, with wifi-hotspot | |
| GPS | Yes | Yes, with A-GPS |
| Speed | | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | Yes, microUSB | microUSB 2.0, USB On-The-Go |
| Camera | Karbonn X21 | Oppo A3s |
| Video Recording | 1080p | |
| Flash | Yes, LED | |
| Main camera | 8 MP with autofocus | 13 MP, Dual |
| Specs | | 13 MP, f/2.2, AF
-2 MP, f/2.4, depth sensor |
| Features | Panorama, Burst Mode, Time Lapse, Face Beauty, Night Mode | LED flash, HDR, panorama |
| Video | | 1080p@30fps |
| Selfie camera | 5 MP with LED Flash | 8 MP, Single |
| Multimedia | Karbonn X21 | Oppo A3s |
| Headphone jack | Yes | |
| Email | Yes | |
| FM Radio | Yes | |
| Music | Yes | |
| 3.5 mm Jack | | Yes |
| Video | Yes | |
| Radio | | FM radio |
| Browser | Yes | |
| Java | No | |
| Design | Karbonn X21 | Oppo A3s |
| Colors | | Red, Dark Purple |
| Dimensions | 147.5 x 71.8 x 9.35 mm | 156.2 x 75.6 x 8.2 mm |
| Weight | 160 g | 168 g |
| Battery | Karbonn X21 | Oppo A3s |
| Battery capacity | 3000 mAh | 4230 mAh, Non-removable Li-Ion |
| Type | Removable Battery | |
| Reverse Charging | Yes | |
| Other | Karbonn X21 | Oppo A3s |
| Release date | | 2018, July |
| Sensors | | Accelerometer, proximity, compass |
