| Hardware and OS | vivo X21 | |
| Operating system | Android 8.1 (Oreo); Funtouch 4 | |
| Processor | Octa-core (4x2.2 GHz Kryo 260 & 4x1.8 GHz Kryo 260) | |
| Chipset | Qualcomm SDM660 Snapdragon 660 (14 nm) | |
| GPU | Adreno 512 | |
| Internal memory | 64/128 GB, 6 GB RAM | |
| External memory | microSD, up to 256 GB (uses SIM 2 slot) | |
| Display | vivo X21 | other phones |
| Type | Super AMOLED | |
| Size | 6.28" inc | |
| Resolution | 1080 x 2280 px | |
| Touchscreen | capacitive touchscreen | |
| Screen-to-Body Ratio | 85.2% | |
| Display area | 98.4 cm2 | |
| Display aspect ratio | 19:9 (height:width) | |
| Pixel Density | 402 PPI | |
| Colors | 16M | |
| Connectivity | vivo X21 | other phones |
| 2G Network | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 | |
| 3G Network | HSDPA 850 / 900 / 1900 / 2100 | |
| 4G Network | LTE band 1(2100), 2(1900), 3(1800), 5(850), 8(900), 34(2000), 38(2600), 39(1900), 40(2300), 41(2500) | |
| Wi-Fi | Wi-Fi 802.11 a/b/g/n/ac, dual-band, WiFi Direct, hotspot | |
| Network | GSM / CDMA / HSPA / LTE | |
| SIM card | Hybrid Dual SIM (Nano-SIM, dual stand-by) | |
| Bluetooth | 5.0, A2DP, LE | |
| Edge | Yes | |
| GPRS | Yes | |
| GPS | Yes, with A-GPS, GLONASS | |
| Speed | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps | |
| USB | microUSB 2.0, USB On-The-Go | |
| Camera | vivo X21 | other phones |
| Main camera | 12 MP, Dual | |
| Specs | 12 MP, f/1.8, 1/2.55', 1.4µm, dual pixel PDAF
-5 MP, f/2.4, depth sensor | |
| Features | LED flash, HDR, panorama | |
| Video | 1080p@30fps | |
| Selfie camera | 12 MP, Single | |
| Multimedia | vivo X21 | other phones |
| 3.5 mm Jack | Yes | |
| Radio | FM radio | |
| Design | vivo X21 | other phones |
| Colors | Black, Aurora White, Ruby Red | |
| Body build | Front glass, aluminum body | |
| Dimensions | 154.5 x 74.8 x 7.4 mm | |
| Weight | 156.2 g | |
| Battery | vivo X21 | other phones |
| Battery capacity | 3200 mAh, Non-removable Li-Ion | |
| Other | vivo X21 | other phones |
| Release date | 2018, March | |
| Sensors | Fingerprint (rear-mounted), accelerometer, proximity, compass | |
