Morse code is the classic example of what this site calls an Encoding: every letter becomes a public pattern, and anyone can undo it — there is no key and no secret. Its purpose is transmission, not secrecy: a message had to survive a wire that could only switch between a click and a silence.
Each letter of the alphabet becomes a short pattern of two signal lengths — the Dot (short) and the Dash (long, three dots long) — and the pattern is chosen so that common letters stay short.
Look the letter up in the table: E, the commonest English letter, gets a single dot; T a single dash; Z gets four symbols.
Send the pattern, then pause one unit to separate letters.
Between words, pause longer — in written Morse, that gap is the
slash: ... --- ... are three letters, .../---/... is a word
boundary.
Digits each get their own five-symbol pattern.
SOS is famous precisely because it is so cheap to send: three dots, three dashes, three dots — with the letter gaps carrying the rhythm.
The tool writes letters with a single space between them and a slash
between words, exactly as above. The two selectors pick which
characters play dot and dash — the encoding is the same, only the
ink changes. In decrypt mode the tool is forgiving: ., * and •
all read as dots, -, _ and ~ all read as dashes, so you can
paste Morse from any source.
The letter lengths are not arbitrary — they are an 1840s frequency analysis. Vail counted letters in a printer's type case and gave the commonest letters the shortest patterns: E is one dot, T one dash, while Q and Z pay four symbols. A message in ordinary English simply takes less airtime. It is the same statistical insight that later powers Frequency analysis — pointed at the wire instead of the cryptogram.
Type your message into the message input. Letters become dot-dash patterns separated by spaces; a space between words becomes a slash.
If you prefer a different look, choose the characters that play dot the dot symbol selector and dash the dash symbol selector — the patterns are unchanged.
Read the encoded line in the output field. Note that unknown characters (punctuation, accents) are dropped — the wire had no use for them either.
Paste the Morse into the message input and press the swap button the swap button.
Keep the format the sender used: one space between letters, a slash between words. Any of the common dot and dash characters are accepted and normalised.
Read the decoded text in the output field. If a letter comes out wrong, look for a missing or doubled space — spacing is where hand-keyed Morse goes wrong.
Compare the patterns from the worked example: E is one unit, T is three. The shortest patterns belong to the commonest letters.
When listening to real Morse, it is the gaps that define letters — an unbroken run of signal means nothing by itself.
This is why operators speak of "dits" and "dahs" with rhythm in their voice: the code was designed for the ear, not the eye.