What Is PWM and Why Is My LED Flickering?

PWM is pulse width modulation. It turns a pin on and off very fast to simulate a lower voltage. The flicker happens when the PWM frequency is low enough for your eyes or camera to notice.

Why flicker happens

Low PWM frequency on some boards.
Short duty cycle values that look like flashes.
Cameras can capture flicker even when your eyes do not.

How to reduce flicker

Increase PWM frequency if your board supports it.
Use a different pin with a higher PWM timer.
For video, use a constant current LED driver.

Bottom line

PWM is fast blinking. If you see flicker, raise the PWM frequency or use a proper LED driver.