When people say "Morse code" today, they almost always mean International Morse Code. It's the version this site uses, and the one standardized for worldwide use. But it wasn't the first.

Two Morse codes

The original code — now called American Morse (or "Railroad Morse") — was developed by Samuel Morse and Alfred Vail in the 1840s for telegraph lines in the United States. It worked, but it had quirks: some letters used internal pauses, and a few used dashes of different lengths, which made it awkward over long distances and noisy connections.

In 1848, a refined version was developed in Germany by Friedrich Clemens Gerke. It removed the odd spacing and variable dash lengths, leaving a cleaner system where every signal is either a dot or a dash of standard length. With small later adjustments, this became International Morse Code, formally adopted at the International Telegraphy Congress in 1865 and later overseen by the International Telecommunication Union (ITU).

The current international reference is Recommendation ITU-R M.1677-1. It lists the character signals, punctuation, procedural signs, and transmission rules used by this site's chart and translator.

What makes it "international"

International Morse Code is defined by a few simple rules that never change:

A dash is three times the length of a dot.
The gap within a character is one dot long.
The gap between characters is three dots long.
The gap between words is seven dots long.

Because those ratios are fixed, a message sent at any speed has the same rhythm — just faster or slower. That consistency is exactly what lets operators around the world read each other regardless of language. For a fuller look at the timing, see Morse code audio and timing.

Where it's still used

Morse code is no longer required for most amateur radio licenses, and satellites have replaced it for official maritime distress. But International Morse Code is far from dead:

Amateur (ham) radio operators still use it — often called CW, for "continuous wave" — because a Morse signal can get through when voice can't.
Aviation navigation beacons identify themselves in Morse.
It remains a reliable fallback for emergency signaling with light or sound.

International Morse versus American Morse

The systems share a name and ancestry, but they are not interchangeable. American Morse used variable dash lengths and internal spaces inside some characters. International Morse limits marks to a one-unit dot and a three-unit dash, giving every operator the same timing model. Several character patterns also differ between the alphabets.

If a modern website, radio manual, or learning course simply says “Morse code,” it almost always means the international system. Historical railroad telegraph material may instead use American Morse, so identify the alphabet before trying to decode an archival message.

Letters outside basic A–Z

The international recommendation includes certain accented characters and procedural signs in addition to the basic Latin alphabet, but national practice and software support vary. The core set used most consistently worldwide is A–Z, digits 0–9, and standard punctuation. Unsupported text should be transliterated deliberately rather than assigned an unofficial pattern.

Try it yourself

The translator on this site implements the International standard, including letters, numbers, and punctuation. Type anything and compare it against the chart — they'll always match, because both come from the same mapping.

International Morse Code Explained