To take a screenshot on an iPhone using buttons, press the Side button (or Top button) and the Volume Up button at the same time, then quickly release both—your screen will flash, and the screenshot will save to Photos. If you prefer using fingers (gestures), go to Settings > Accessibility > Touch > Back Tap, then set Double Tap or Triple Tap to “Screenshot”—now just tap the back of your iPhone with your finger to capture the screen.