How to make a UIView glow using shadowColor

Swift version: 5.2

Paul Hudson @twostraws May 28th 2019

All views can have shadows thanks to the CALayer behind them, but you can use that same property to create glow effects. For example, this creates a 128x128 view then gives it a 20-point yellow glow:

let vw = UIView(frame: CGRect(x: 100, y: 100, width: 128, height: 128))
vw.backgroundColor = .white

vw.layer.shadowOffset = .zero
vw.layer.shadowColor = UIColor.yellow.cgColor
vw.layer.shadowRadius = 20
vw.layer.shadowOpacity = 1
vw.layer.shadowPath = UIBezierPath(rect: vw.bounds).cgPath

Bright glows work best on a dark background, so try making your main view black: