Morse Code Decoder

Written Morse looks compact because the message has already been reduced to marks and separators. A dot or dash by itself is not enough to identify a letter; the reader also needs to know where one character ends and where the next word begins. The same marks can decode cleanly or turn into nonsense depending on whether spaces, slashes, line breaks, or custom dividers have been copied faithfully.

International Morse code is a codebook, not a cipher. Each supported written character has a fixed dot-dash group, such as ... for S, --- for O, and .---- for 1. Decoding reverses that lookup. The difficult part in ordinary copied text is usually not the letter map, but the boundaries around it: extra spaces, missing slashes, pasted punctuation, or worksheet separators can change the groups before the lookup even starts.

Timing terms still matter after Morse has been written down. In sound or light, a dot is one time unit, a dash is three units, the gap between letters is three units, and the gap between words is seven units. In a plain text transcript, those gaps become conventions. A single space often separates letters, while a slash often separates words. Some practice sheets use pipes, double spaces, or custom markers instead, so a reliable decode starts by matching the separator convention used by the source.

A decoded sentence is therefore only as trustworthy as its grouping. Clean text with one skipped group can hide a missing character, while replacement markers make errors noisier but easier to audit. For lessons, log cleanup, puzzle answers, or copied-message review, check both the readable text and the normalized Morse before treating the result as final.

How to Use This Tool:

Start with the separator convention, then refine the readable output and audio settings once the parse is correct.

1. Paste written Morse into Morse code, or use Browse TXT to load a plain text file. The decoder uses the first non-blank line and reports later non-blank lines as ignored.
2. Set Letter separator to the marker between character groups. Use space for input like .... . .-.. .-.. ---, or enter the exact custom divider used in the source.
3. Set Word separator to the marker between words. The default slash matches common written Morse such as .... . .-.. .-.. --- / .-- --- .-. .-.. -...
4. Choose Unknown token policy. Replacement keeps a visible placeholder in Decoded Text, while skip removes unrecognized groups and can make a damaged message look cleaner than it is.
5. Use Case mode, Output letter separator, and Output word separator after Unknown tokens looks right. These settings format the result and normalized Morse; they do not make invalid groups valid.
6. Adjust Audio speed, Farnsworth speed, Tone frequency, Volume, Lead silence, and Tail silence when you want the decoded pattern as practice playback or a WAV file.

If the output is blank, merged, or full of placeholders, check Letter separator and Word separator first. Separator mistakes change the groups before any codebook lookup happens.

Interpreting Results:

Decoded Text is the readable answer, but it should be reviewed with Unknown tokens and Normalized Morse. A zero unknown count and a normalized line that matches the intended grouping are the strongest signs that the text decode is reliable.

A readable sentence can still be wrong when a separator merged two letters into one valid-looking group. When the result matters, compare Decoded Text against Normalized Morse, then inspect any placeholder or unknown count before copying the text into notes or training material.

Technical Details:

International Morse code assigns dot-dash groups to letters, figures, and selected punctuation. The written group is case-insensitive because dots and dashes carry the character identity; output case is a later formatting choice. Separators are not part of the codebook, but they decide which mark runs become lookup tokens.

A written decoder has two separate jobs. First it must normalize copied marks and split the line into tokens. Then it can look up each token in the codebook and preserve enough diagnostics to show whether the parse was trustworthy. Unknown groups are especially important because they can represent a typo, a prosign not covered by the character map, a copied separator error, or a real source mark that needs manual review.

Transformation Core:

Codebook Core:

The supported map covers A to Z, digits 0 to 9, and common punctuation including period, comma, question mark, apostrophe, exclamation mark, slash, parentheses, ampersand, colon, semicolon, equals, plus, hyphen, underscore, quotation mark, dollar sign, and at sign. Operational prosigns and special signals that do not share one of those supported written characters should be treated as unknown unless the source has already expanded them into ordinary characters.

Timing Core:

Morse timing is built from a dot unit. The common PARIS words-per-minute convention treats one standard word as 50 dot units, so a dot at character speed WPM is 1.2 / WPM seconds. A dash is three dot units. Farnsworth timing keeps the character marks at the selected character speed while widening the gaps between letters and words when the Farnsworth speed is lower than the character speed.

At 20 WPM, one dot unit is 0.06 seconds and one dash is 0.18 seconds. If Farnsworth is set to 8 WPM, the dots and dashes keep the 20 WPM length while the letter and word gaps use a 0.15-second gap unit. Lead silence, tail silence, and the final off segment in the generated tone plan can make Audio seconds slightly longer than a textbook count of only marks and inter-character gaps.

Privacy Notes:

The Morse text, decoded output, charts, audio preview, and WAV rendering are handled in the browser after the page loads. The message can also be reflected in shareable page settings, so avoid sharing the address when the Morse text itself is sensitive.

This is a written-Morse decoder. It does not listen to a microphone, analyze recordings, or read a waterfall trace. Audio, light, or hand-keyed material must be transcribed into dots, dashes, and separators before it can be decoded here.

Worked Examples:

Default classroom phrase. With .... . .-.. .-.. --- / .-- --- .-. .-.. -.., a space as Letter separator, and / as Word separator, Decoded Text becomes HELLO WORLD. Unknown tokens should be 0, and Normalized Morse should preserve the same groups with the chosen output separators.

Custom worksheet dividers. A line such as ....|.|.-..|.-..|---#.--|---|.-.|.-..|-.. needs | as Letter separator and # as Word separator. If those fields are left at their defaults, the grouped marks will not split correctly and Unknown tokens will rise.

Damaged or unsupported group. If ... --- ... / ........ is decoded with replacement enabled, Decoded Text keeps a placeholder for the eight-dot group and Unknown tokens shows 1. Treat that as a review flag rather than silently accepting the readable part of the message.

FAQ:

Glossary:

Dot or dit

The short Morse mark and the base timing unit for playback.

Dash or dah

The long Morse mark, equal to three dot units in standard timing.

Token

One parsed dot-dash group that is looked up as a letter, digit, or punctuation mark.

Letter separator

The written boundary between Morse character groups.

Word separator

The written boundary between Morse words, often shown as a slash.

Farnsworth timing

A practice timing method that keeps characters fast while widening the spaces between letters and words.

Normalized Morse

The recognized groups rebuilt with consistent output separators.

References:

• Recommendation ITU-R M.1677-1: International Morse code, International Telecommunication Union, October 2009.
• A Standard for Morse Timing Using the Farnsworth Technique, ARRL QEX, April 1990.
• Morse Code Timing, MorseCode.World.