SOS is the most recognised distress signal in the world — and it works with almost anything that can be turned on and off: a flashlight, a radio, a mirror catching sunlight, even a whistle.
The pattern
SOS in Morse code is:
· · · — — — · · ·
Three short signals, three long signals, three short signals, repeated. Each "short" (a dot) and "long" (a dash) has a specific timing relationship — a dash is three times the length of a dot, and there are precise gaps between symbols, letters, and the repeated word.
Why SOS specifically?
Contrary to popular belief, SOS doesn't stand for "Save Our Ship" or "Save Our Souls" — those are backronyms invented after the fact. SOS was chosen in 1906 as an international distress signal because its Morse pattern (three short, three long, three short) is simple, unmistakable, and easy to send correctly even under stress or with unfamiliar equipment. It also reads the same forwards and backwards, which helps it stay recognisable even if reception is partial.
Why a flashlight works
Morse code doesn't care what's making the signal — light, sound, or radio waves all work the same way, since it's just a pattern of "on" and "off" over time. A blinking flashlight sending the SOS pattern is a legitimate, internationally recognised way to signal distress, especially at night or across open water or terrain where a light source is visible from a distance.
Try it
The free Flashlight tool has a one-tap SOS button that blinks the exact standard pattern and timing automatically — using your screen as a light source on any device, or your phone's real camera flash where the browser supports it.