The instrument‑panel warning light that shows your headlights are on main beam is the small blue headlamp symbol, usually shaped like a headlight with several horizontal lines pointing straight ahead.

What the main beam warning light looks like

On almost all modern cars:

  • It is blue.
  • It looks like a headlamp icon with straight, horizontal “light beams” pointing to the left (in UK‑style graphics).
  • It only illuminates when your high / full / main beam is switched on, not just side lights or dipped beam.

A simple way to picture it: if the dipped‑beam symbol is green with lines dropping downwards, the main‑beam one is blue with lines pointing straight out.