How Morse code encodes letters
Morse represents each character as a sequence of short and long signals, traditionally called dits and dahs and written as dots and dashes. The assignment is not arbitrary: Samuel Morse and Alfred Vail counted the type in a printer's case to estimate letter frequency in English and gave the commonest letters the shortest codes. E is a single dot, T a single dash, A is dot dash, and rarely used letters such as Q get four symbols.
That frequency weighting is the same principle behind modern variable-length codes such as Huffman coding, arrived at nearly a century earlier by counting type. It is why Morse is faster to send in English than a fixed-length code of the same alphabet would be.
This translator covers the 26 Latin letters, the ten digits and the punctuation defined in the international standard, including period, comma, question mark, apostrophe, exclamation mark, slash, parentheses, ampersand, colon, semicolon, equals, plus, hyphen, underscore, quotation mark, dollar sign and at sign. The at sign is the newest addition, adopted in 2004 to make email addresses sendable.
Timing is what makes Morse readable
The written dots and dashes are a transcription of something fundamentally temporal. The dit is the base unit. A dah lasts three units. The gap between symbols within a letter is one unit, the gap between letters is three units, and the gap between words is seven. Those ratios, not the absolute speed, are what an operator's ear locks onto.
In text form the timing is expressed by spacing, and this tool follows the common convention: a single space separates the symbols of adjacent letters and a slash with spaces around it separates words. So SOS is ... --- ... and HELLO WORLD is .... . .-.. .-.. --- / .-- --- .-. .-.. -.. with each letter's symbols kept together.
Getting this wrong is the usual source of confusion, because the same symbol string means different things depending on where the gaps fall. ... - is S followed by T, while ...- with no gap is the single letter V. In audio, a sender whose letter gaps are too short produces exactly this ambiguity, which is why timing discipline matters more than speed.
Prosigns, SOS and what this tool does not cover
SOS is not an abbreviation of save our ship or anything else. It was chosen in 1906 for its distinctive unbroken rhythm, three dots, three dashes, three dots sent as a single symbol with no letter gaps. Written as a prosign it is often shown with an overbar. Because this tool works letter by letter, typing SOS produces ... --- ... with letter gaps, which is the written convention rather than the continuous emergency signal.
Other prosigns work the same way: AR for end of message, SK for end of contact, BT as a section separator. Each is two letters run together without the usual gap, and none of them can be expressed in a letter-by-letter translator. Amateur radio operators also use a large set of abbreviations and Q codes, such as QTH for location and QRZ for who is calling, which are ordinary letters and translate normally.
The translator handles the Latin alphabet only. Extended sets exist for accented letters in several European languages, for Greek, Cyrillic, Hebrew and Arabic, and Japanese uses an entirely separate system called Wabun that maps kana rather than letters. Characters with no mapping are dropped from the output rather than passed through, so check the result if your input contains anything unusual.
Why Morse is still in use
Morse survives because it is extraordinarily robust. A signal that is barely distinguishable from noise can still be read by ear when it carries only two states, which means Morse gets through on power levels and in conditions where voice is unintelligible. That is why amateur radio operators still use it for weak-signal work and long-distance contacts on low power.
It requires almost nothing to send. A flashlight, a mirror, a whistle, a car horn, a finger tapping on a table or a single switch wired to anything can carry it, which is why it appears in survival training and emergency procedure. Aviation still uses it for navigation beacon identifiers, which broadcast their two or three letter code continuously.
It also has a place in accessibility. Morse input allows text entry from a single switch, which makes it a viable interface for people with very limited motor control, and both major mobile platforms include Morse input options in their accessibility settings.