Visual SOS and Morse Code: Patterns, Controls, and Signaling Limits

SOS uses three short flashes, three long flashes, then three short flashes: ···−−−···. You can use a light to show the pattern, but a viewer must see and recognize it. Prioritize contacting emergency services if you can, and preserve phone charge for communication.

Morse Timing

Use a dot as the base timing unit:

Element	Duration
Dot	1 unit
Dash	3 units
Gap within a letter	1 unit
Gap between letters	3 units
Gap between words	7 units

For a 200-millisecond dot, a dash lasts 600 milliseconds. The app’s standard SOS mode uses that dot length with gaps between the S, O, and S groups, then a pause before repeating. Browser timers and display refresh can alter the visible timing; the tool is not a certified signaling device.

Alphabet and Numbers

Use these tables to check a short message before signaling.

Character	Code	Character	Code
A	·−	N	−·
B	−···	O	−−−
C	−·−·	P	·−−·
D	−··	Q	−−·−
E	·	R	·−·
F	··−·	S	···
G	−−·	T	−
H	····	U	··−
I	··	V	···−
J	·−−−	W	·−−
K	−·−	X	−··−
L	·−··	Y	−·−−
M	−−	Z	−−··

Number	Code
0	−−−−−
1	·−−−−
2	··−−−
3	···−−
4	····−
5	·····
6	−····
7	−−···
8	−−−··
9	−−−−·

Start SOS or Custom Morse

1. Open the flashlight tool and its SOS panel.
2. For standard SOS, tap the Active button marked OFF to start. Tap ON to stop.
3. For a custom message, select Custom Morse Code, enter text, choose a speed, and check the displayed code.
4. Press START to begin custom Morse and STOP to end it.

Starting either mode turns the light on if needed.

Typing does not start flashing. Keep a custom message short and check its characters before use. Choose a message the intended viewer can understand; arbitrary text is not a distress signal.

Visibility Limits

Face the screen toward the intended viewer if you can do so without moving into danger. Weather, ambient light, obstacles, distance, and viewing angle affect what they can see. Do not assume a fixed range or move to a hazardous position to improve a signal.

Use suitable dedicated signaling equipment if available. A browser screen cannot guarantee that rescuers will notice or understand it. For someone nearby, steady light or readable marquee text may be enough.

Flashing Precautions

SOS and Morse expose viewers to flashing light, which can trigger seizures in people with photosensitive epilepsy. Avoid exposing anyone who may be photosensitive. Warn others nearby and get their consent; no speed setting guarantees safety. Read the strobe safety guide.

Avoid pointing bright light into someone’s eyes. If you need nearby illumination in darkness, our red light guide covers dim settings and their limits.

Preserve Charge

Use short signaling attempts if you need to conserve battery, and keep enough charge for calls, messages, and alerts. A spare device can provide light while you reserve your primary phone for communication.

Our battery guide covers settings and preparation. The emergency lighting guide explains backup lights you can test before an outage.