What is the ITU-R Morse standard?

ITU-R Recommendation M.1677-1 defines international Morse code: the dot and dash patterns for letters, digits, and punctuation, plus the timing rules. This tool uses that standard set rather than older American Morse variants.

A prosign is a procedural signal sent as a single run-together symbol with no gap between its letters. Examples are SOS (the distress call), AR (end of message), SK (end of contact), BT (a pause or new section), and BK (break).

How do I separate letters and words in Morse?

Put a single space between the code for each letter and three spaces, or a forward slash, between words. The decoder accepts either word separator and shows decoded words separated by a single space.

Why does SOS decode differently from S O S?

Sent as the prosign SOS the pattern is one continuous symbol with no internal gaps, dot-dot-dot-dash-dash-dash-dot-dot-dot, and the tool recognises it as the distress signal. Sent as three separate letters with gaps it decodes as the plain letters S, O, S.

Is my text processed locally?

Yes. Encoding and decoding use a built-in lookup table in your browser, so nothing you type is uploaded or stored anywhere.

ITU-R Morse with Prosigns

This tool encodes and decodes ITU-R international Morse code and, unlike a plain A to Z chart, understands the run-together prosigns and operating signals used in real radio traffic, such as the distress call SOS, the end-of-message AR, and the end-of-contact SK. Type text to get Morse, or paste Morse to read it back.

How it works

Each letter, digit, and punctuation mark maps to a fixed pattern of dots and dashes from ITU-R M.1677-1. The spacing rules carry the structure:

between symbols in a letter : (none)
between letters             : one space
between words               : three spaces  (or a / )
prosign (e.g. SOS, AR, SK)  : letters run together with NO internal gap

On encode, the tool joins each letter’s pattern with single spaces and each word with three spaces. On decode, it splits on spacing, looks each symbol up in the reverse table, and first checks whether a gapless symbol matches a known prosign. Recognised prosigns are shown in angle brackets such as <SOS> and <AR>; unknown symbols decode to a replacement marker.

Notes and example

Encoding SOS GERA gives ...---... --. . .-. .-, and decoding the gapless ...---... returns <SOS>. Note that several prosigns share a pattern with a punctuation mark: .-.-. is both the AR end-of-message prosign and the plus sign, and -...- is both BT and the equals sign, so context decides the intended meaning. The output is plain text and copies cleanly into chat, notes, or radio logs.