How to signal SOS: tap, flash, blink or sound it

An SOS in Morse code is a signal to the people who can see or hear you. It is not a call: it reaches nobody on its own, and it only works if someone notices it and understands it. So when your phone works, use the phone.

• Dial the emergency number. That is 911 in the US. In the EU, 112 reaches the ambulance, fire brigade or police in every country, and it works on GSM mobile networks worldwide.
• Or use your phone's Emergency SOS. On an iPhone, press and hold the side button and either volume button until the countdown ends (everywhere except India), or turn on Call with 5 Presses in Settings > Emergency SOS and press the side button five times. The iPhone calls emergency services. After the call ends, it texts your emergency contacts, with your location if it's available, unless you cancel. On Android 12 and later, press the power button 5 times or more, then, depending on your settings, touch and hold the red circle for 3 seconds or wait for the countdown. Android's Emergency SOS doesn't work in airplane mode or with Battery Saver on.

Use the Morse signal when you can't call: no signal, no phone, no voice. Or use it alongside the call, to show rescuers where you are once they are close.

Send it only when someone is in danger. In the US, federal law (47 U.S.C. § 325) says no one may knowingly send a false or fraudulent distress signal, and the European Commission warns that hoax 112 calls can be a criminal offense in most countries. For where Morse code is still heard today, see Is Morse code still used?

Whatever you send it with, the pattern and the steps are the same:

1. 1Three short signals.
2. 2Three long signals, each about three times as long as a short one.
3. 3Three short signals.
4. 4Keep the gaps inside the signal short, about as long as a short signal. Don't stop between the S, the O and the S: SOS is one signal of nine parts, not three letters.
5. 5Pause.
6. 6Repeat until someone answers.

Written down, it is ...---.... A line over the letters shows they are sent as one unbroken signal. What SOS means, why it was chosen and how the Titanic used it are on SOS in Morse code.

How long is "short"? One short signal is one unit. One unit lasts 1,200 ÷ WPM milliseconds, where WPM is the sending speed in words per minute. SOS is 23 units long. By hand, about 5 WPM is easy to keep and easy to read:

The exact speed matters less than a clear difference between short and long. Someone watching from a distance needs to see three, three and three, short-long-short.

A knock is over the moment it lands, so you can't make a knock long. To tap SOS on a wall, pipe or table, use the spacing instead:

1. 1Knock three times, quickly.
2. 2Knock three times, slowly, with longer gaps between the knocks.
3. 3Knock three times, quickly.
4. 4Pause, then repeat.

On a touchscreen or a key, you can hold. Tap SOS with your finger as three quick taps, three held presses and three quick taps. The Morse keyboard reads it the same way: in Tap mode a quick press is a dot and a hold is a dash, and it shows the letters as you key them, so you can check your SOS.

Tap code works without long knocks. Each letter is two groups of knocks: its row, then its column on a 5 by 5 grid. SOS in tap code is 4-3, 3-4, 4-3: four knocks and three knocks for S, three and four for O, then S again. The tap code translator knocks it out loud so you can hear the rhythm.

If you are trapped. The American Red Cross says to signal for help with a whistle, or to knock loudly on a solid piece of the building three times every few minutes, because rescue personnel listen for such sounds. It also says to protect your mouth, nose and eyes from airborne debris. The CDC says to try to get someone's attention by tapping on hard or metal parts of the structure. Neither asks for SOS in particular: knocking or tapping is the advice, and SOS is one pattern people recognize.

1. 1Point the light toward whoever might see it.
2. 2Flash three short flashes, three long flashes and three short flashes, with a short dark gap between flashes.
3. 3Stay dark for a moment, then repeat.

Some flashlights have an SOS mode that flashes 3 short, 3 long, 3 short on its own. Any light you can switch on and off will do, car headlights included.

With your phone, the flashlight signaller keeps the timing for you:

1. 1Open it. SOS is already loaded as one signal.
2. 2Choose the light. On most Android phones in Chrome it can flash the phone's flashlight; it asks for camera access once. iPhone and iPad browsers don't let websites switch the flashlight on, so there it flashes the whole screen, which works on any device.
3. 3Turn on Repeat until stopped, so it keeps sending.
4. 4At night, choose the red flash colour: the screen flashes red instead of white.

The screen and the lamp on the page stay at 7 WPM or slower, under 3 flashes a second, to protect people with photosensitive epilepsy; the flashlight can go up to 15 WPM. Before the screen starts, the tool warns you that it will flash. Press Esc, go back or tap Stop to end it.

One caution from a hiking guide: you may need your phone to call mountain rescue, so don't run its battery down on light. Carry a small flashlight or headlamp for signaling.

1. 1Blink three times, quickly.
2. 2Blink three times slowly, holding your eyes shut a little longer each time.
3. 3Blink three times, quickly.
4. 4Pause, then repeat.

Three blinks on their own are only an S. The three long blinks in the middle are what make it SOS.

Blinking works when someone can see your face but you can't speak or move freely, for example on a camera or a video call. It has a famous precedent: in 1966 Jeremiah Denton, a US Navy pilot held as a prisoner of war in North Vietnam, was forced into a televised interview and blinked the word T-O-R-T-U-R-E in Morse code, confirming for the first time to US Naval Intelligence that American prisoners were being tortured.

Whistle. Blow three short blasts, three long and three short, and repeat every minute. A whistle can reach more than 120 decibels with little effort, while keeping up a loud shout takes a lot of effort and can cost you your voice. In mountain areas you may hear the Alpine distress signal instead: six blasts in quick succession, repeated once a minute. The answer to either is three blasts, to tell the person in trouble they have been heard. At sea, SOS sent by sound, on a horn for example, is one of the recognized distress signals.

Mirror. A flash of sunlight from a mirror is a recognized distress signal at sea. A signal mirror has a sighting hole to aim it; with an ordinary mirror, use your fingers as a sight, though that is less accurate. The reflected beam is less than a degree wide, so aim carefully.

Arms. At sea, raising and lowering both outstretched arms slowly and repeatedly is one of the recognized distress signals.

On the ground. Spell out the letters SOS large enough to see from the air: stamped in snow, or made from logs on a beach. SOS reads the same upside down, which makes it easier to recognize.

By touch. The vibration pattern tool buzzes a message on Android phones that can vibrate in the browser. iPhone browsers can't vibrate, so it guides you to record the pattern as a custom vibration in Settings, Sounds & Haptics.

Practice indoors, where nobody could take it for a real call for help. The flashlight signaller's Preview here button plays SOS on a lamp on the page, so you can watch the rhythm without flashing anything. Say it as you go, "di-di-di-dah-dah-dah-di-di-dit", and the pattern sticks. To learn the rest of the code, start with how to learn Morse code.

Open the flashlight signaller with SOS loaded, press Preview here to watch the rhythm, then send it with your phone's flashlight or screen. To hear SOS as one signal and as three letters, play it on SOS in Morse code.

This guide is written and kept up to date by Translate Morse Code (independent site). Every timing on it was computed with the site's own Morse engine, every tool feature was checked in the tools' code, and every safety statement was checked against the source listed below.