Morse Code Converter, Text to International Morse Code

Morse code is one of the oldest digital communication systems still in active use. From the first telegraph line between Washington and Baltimore in 1844 to the amateur radio bands of today, the simple pattern of short tones (dots) and longer tones (dashes) has transmitted distress calls, military orders, navigation beacons, and casual conversations across every ocean and continent for nearly two hundred years. This page explains what Morse code is, where it came from, how the timing rules were standardised, and how to use the bidirectional text ⇄ Morse converter at the top of this page to encode, decode, and listen to Morse code in any modern browser.

The converter above lets you type plain text and watch it appear as dots and dashes in the second box, or type dots and dashes and watch them turn back into plain text. Both directions update live as you type. You can switch between standard spacing (slash between words) and continuous form, copy either side to your clipboard, and play the message back as audio at any speed between five and twenty-five words per minute. Eight presets cover the common use cases: SOS, HELLO, the QUICK BROWN FOX pangram, the full alphabet, the full digit set, MAYDAY, and the CQ calling sequence used by amateur radio operators to invite any station to reply.

History of Morse code

The code was developed in the United States during the 1830s and 1840s by two men, the painter and inventor Samuel F. B. Morse, whose name the code carries, and his assistant Alfred Vail, who did most of the actual signal design. The pair filed a patent in 1840 and demonstrated the device to the United States Congress in 1844. The first operational telegraph line ran sixty-four kilometres from Washington, D.C. to Baltimore, Maryland, and the very first official message sent over it was the now-famous sentence "What hath God wrought", taken from the Book of Numbers.

The original code was very different from what we use today. Vail's first table assigned short numbers to common English words, "1" meant "the", "2" meant "a", and so on, and longer numbers to rarer words, all sent as a single coded number per word. This was efficient for the small vocabulary of an experimental telegraph but useless for general communication. By the late 1840s the system had been reworked into the per-letter code we recognise today: each letter of the alphabet, each digit, and a small set of punctuation marks were given their own short pattern of dots and dashes.

From the United States the telegraph spread across Europe within ten years. Operators discovered almost immediately that they could understand messages faster by listening to the sound of the sounder than by reading the printed tape. This led to a series of refinements that turned the dot/dash paper code into a true audio code, with standardised timings, abbreviations, and procedural signals.

The timing rules, Paris 1865 standard

The most important standardisation came at an international conference in Paris in 1865. Telegraphers from every major European country agreed on the durations of the dot, the dash, and the three kinds of gaps. The convention is often called the Paris standard or the HAM standard and is still the basis for every Morse timing measurement today.

Under the Paris standard one dit (a dot) is the fundamental unit. Every other duration is expressed as a multiple of one dit:

• one dit, a dot
• one dah (a dash), three dits long
• intra-character gap, the silence between dots and dashes inside one letter, one dit
• inter-character gap, the silence between two letters in the same word, three dits
• inter-word gap, the silence between two words, seven dits

At a sending speed of fifteen words per minute (the most common speed for trained operators and the default in this tool) the dit lasts 80 milliseconds, the dah 240 milliseconds, the intra-character gap 80 milliseconds, the inter-character gap 240 milliseconds, and the inter-word gap 640 milliseconds. Slower speeds stretch every duration proportionally; faster speeds compress them. A speed of twenty-five words per minute produces a dit of about 48 milliseconds, which is at the upper limit of comfortable hand-keying and well within the range of modern electronic keyers and decoders.

The words-per-minute figure itself comes from the word "PARIS", which conveniently contains all the timing elements. Sending "PARIS" at one word per minute takes fifty dits: forty-three dits of tone and seven dits of gap. So one word per minute equals fifty dits per minute, and fifteen words per minute equals 1200 ÷ 15 = 80 milliseconds per dit.

Common prosigns and abbreviations

Experienced operators do not send every letter of every word. They use prosigns, procedural signals with no letter equivalents, and conventional abbreviations to speed up routine exchanges.

• SOS, ... --- ..., the international distress call, sent as a single continuous run with no inter-character gaps. Adopted at the 1906 International Radiotelegraph Convention in Berlin. Although the letters S, O, and S were chosen because they are easy to send (no spaces, no special punctuation), the meaning is "save our souls" or "save our ship" only by convention; SOS is itself the signal, not an abbreviation.
• MAYDAY, the voice distress call derived from the French m'aider (help me). In Morse, Mayday is just the letters M-A-Y-D-A-Y, which run together as -- .- -.-- -.. .- -.--.
• CQ, --.- --.-, "calling any station". Used by amateur radio operators to invite any other station to respond. A long CQ call ("CQ CQ CQ DE …") means the operator is actively looking for a contact.
• K, -. -, "over to you" or "any station go ahead". Sent at the end of a transmission to invite a reply.
• SK, ... -.-, "end of contact" or "silent key". Sent before signing off.
• 73, --... ----.--, "best regards". A general-purpose sign-off expressing goodwill.
• 88, ---.. ---.., "love and kisses". The Morse equivalent of an affectionate hug.
• QRS, --.- .-. ..., "please send slower". Used when one station cannot keep up.
• QRQ, --.- .-. --.-, "please send faster". Used when one station wants a higher speed.
• QTH, --.- - ...., "what is your location?" or "my location is …".

Because the converter above handles full text, you can paste any of these prosigns in as letters and they will round-trip correctly. There is no special handling for prosigns in the encoder because the prosign's meaning is carried by the spacing, not by any special character: SOS is "S-O-S" with no inter-character gaps, not "S O S" with spaces. If you want to send SOS in continuous form using this tool, paste SOS into the Text box and toggle the spacing mode to continuous.

Prosigns versus letters

A frequent point of confusion for beginners is the difference between a prosign and a letter. In the printed representation on paper tape, a prosign was written by running the letters together with no visible separator. In modern text-based representations (and in this tool) prosigns are usually just shown as their constituent letters with a comment explaining the meaning. The fact that they "look like" ordinary letters is the entire point: prosigns do not need a new code, they are just shorter or differently-spaced sequences.

The most common prosign-confusion is between 6 (-...., one dah followed by five dots) and the prosign error (........, eight dots). When an operator makes a mistake mid-sentence, the convention is to send eight dots in a row as an apology and then re-transmit the word. Eight dots happens to be one longer than the digit 6, so beginners sometimes decode error-prosigns as a number followed by a couple of dots.

Modern uses of Morse code

Although its share of the world's communication traffic has shrunk to almost zero, Morse code is still actively used in several niches:

• Amateur radio, many national regulators (including the United States Federal Communications Commission since 2007) have removed the Morse proficiency test for the entry-level amateur radio licence, but Morse is still extremely popular on the HF bands. Contesters routinely operate at thirty words per minute or faster. The automatic digital modes PSK31 and FT8 are now more popular for weak-signal work, but Morse retains a place because a skilled operator can often pull a Morse signal out of noise that a digital decoder cannot.
• Aviation beacons, non-directional beacons (NDBs) at airfields around the world still identify themselves with a three-letter Morse identifier every few seconds. A pilot tuning a radio receiver can confirm the station by listening for the identifier. The conversion of these beacons to modern GPS-based approaches is gradual and incomplete.
• Maritime distress, the global maritime distress and safety system (GMDSS) replaced the traditional 500 kHz Morse channel in 1999, but Morse on 500 kHz and 2182 kHz is still authorised as a backup and is still monitored by some volunteer organisations.
• NATO emergency signals, the armed forces of several NATO countries still train Morse operators for low-probability-of-intercept communications and for emergency use when radio silence is required.
• Assistive technology, people with severe motor impairments can use single-switch Morse input as an alternative to a keyboard or a sip-and-puff interface. The same encoder/decoder pipeline that powers this tool is also used in many Morse-based AAC devices.
• Education and hobbies, learning Morse remains a popular hobby, partly because it is a rare example of a complete human skill (send, receive, copy, transcribe) that can be practised without any internet connection.

Common mistakes when reading or sending Morse code

A few errors come up so often that they deserve to be called out:

1. Confusing six with error-prosign. The digit 6 is -.... (one dah then five dots). The error prosign is ........ (eight dots). When you read Morse on paper, the length of the run of dots is the only thing that distinguishes them. Always count.
2. Treating the slash as data. In this tool a forward slash marks a word boundary, not a letter. Some texts write Morse with no slash and rely on the reader to infer word boundaries from the inter-character gap. If you paste such text into the decoder the result will have no spaces between words. Toggle the spacing mode to continuous before pasting.
3. Sending dah as a stretched dot. A dah is three dits long, not five, not two. Beginners often send dahs that are too long because they sound "more emphatic". This is one of the first things a Morse teacher will correct.
4. Forgetting the inter-character gap. Letters within a word must be separated by three dits of silence, not by a one-dit gap. A one-dit gap will be heard by a trained operator as another dit of the same letter, garbling the message.
5. Running letters together when sending a prosign. SOS, MAYDAY, and similar distress calls are sent as one continuous run with no intra-character gaps and no inter-character gaps. Beginners often slow down and send SOS as ... / --- / ... with full word spacing, which is incorrect and harder to identify by ear.

How the converter works

The encoder takes any input string and walks through it one character at a time. Letters and digits are looked up in a table that maps each one to its dot-dash sequence. Punctuation marks are looked up in the same table, period is .-.-.-, comma is --..--, question mark is ..--.., and so on. Whitespace runs in the input are converted to word boundaries in the output, which are written as a slash surrounded by spaces. Any character not in the table is replaced with a literal ? so the user can see where the gap occurred.

The decoder does the same thing in reverse. It splits the input on whitespace, looks up each token in the reverse table, and assembles the result. A token containing a forward slash is treated as a word boundary, so the decoder accepts both standard form (with slashes between words) and continuous form (with no slashes) without any explicit conversion.

The audio scheduler walks the same encoded string and builds a flat list of "tone" and "gap" events. Each tone event is a short sine-wave burst at the chosen frequency (default 600 Hz). Each gap event is silence. The total duration is computed from the sum of all event durations. At the user-chosen words-per-minute speed, a dit lasts 1200 ÷ wpm milliseconds, a dah three times that, an intra-character gap one dit, an inter-character gap three dits, and an inter-word gap seven dits. The Web Audio API schedules all events on a single OscillatorNode with the gain gated on for tones and off for gaps, so playback is sample-accurate regardless of how fast the React rendering loop is running.

International Morse Code, the complete table

The table below lists every character supported by this converter. Letters and digits are exactly the ITU-R M.1677-1 (2009) recommendation. Punctuation marks follow the same recommendation with the same codes every modern implementation uses.

Letters (A-Z)

A .- B -... C -.-. D -.. E . F ..-. G --. H .... I .. J .--- K -.- L .-.. M -- N -. O --- P .--. Q --.- R .-. S ... T - U ..- V ...- W .-- X -..- Y -.-- Z --..

Digits (0 to 9)

0 ----- 1 .---- 2 ..--- 3 ...-- 4 ....- 5 ..... 6 -.... 7 --... 8 ---.. 9 ----.

Punctuation

. .-.-.- , --..-- ? ..--.. ' .----. ! -.-.-- / -..-. ( -.--. ) -.--.- & .-... : ---... ; -.-.-. = -...- + .-.-. - -....- _ ..--.- " .-..-. $ ...-..- @ .--.-.

Why Morse survives

It is fair to ask why a two-centuries-old code is still in use when modern digital systems can send any message at many times the speed. The answer is that Morse has three properties that turn out to be valuable in niches where digital systems fail.

First, a skilled operator can copy Morse in noise that would defeat any digital decoder. A human brain is exceptionally good at picking out a repeating pattern from background static. Digital modes that use a fixed bit rate need a much higher signal-to-noise ratio to be readable.

Second, the bandwidth is essentially zero. A CW (continuous-wave) Morse transmission occupies roughly the bandwidth of its keying speed, a 15 wpm signal fits in about 50 Hz of spectrum. A voice transmission occupies 2,400 Hz. An FT8 digital signal occupies 50 Hz but only carries a structured message. Morse wins on simplicity.

Third, the equipment is trivial. A Morse transmitter is just an oscillator that the operator turns on and off. A receiver is just an oscillator that the operator listens to. There is no modem, no protocol stack, no encryption, no error correction. For emergency use in a remote area this matters: a fifty-dollar handheld radio and a hand key will get a distress call out under conditions that would defeat any consumer smartphone.

Worked examples

1. Encoding the word "SOS". Each letter maps to its code: S is ..., O is ---, S is .... With standard spacing the encoder writes ... --- ... (no slash, because there is no word boundary). At 15 wpm a dit is 80 ms, a dah is 240 ms, the intra-character gap is 80 ms, and the inter-character gap is 240 ms. The whole signal takes 9 elements (3 dits and 3 dahs per letter across 3 letters) plus the character gaps: 9 × 80 ms of dits/dahs plus 2 × 240 ms of character gaps, about 1.2 seconds in total.

2. Decoding a word boundary. The input .... . .-.. .-.. --- / .-- --- .-. .-.. -.. contains a slash between "HELLO" and "WORLD". The decoder treats the slash as a word boundary, so the output is "HELLO WORLD", not "HELLOWORLD". In continuous form the same text is sent as .... . .-.. .-.. --- .-- --- .-. .-.. -.. (no slash) and the decoder still returns "HELLO WORLD" because it infers the word boundary from the longer silence in the audio stream.

3. Timing check at different speeds. At 20 wpm a dit is 1200 ÷ 20 = 60 ms. The same "SOS" signal now takes about 0.9 seconds. The audio scheduler derives every gap from the chosen speed, so the code pattern stays identical while the playback tempo changes.

References

• ITU-R M.1677-1 (2009), International Morse code, the recommendation that defines the letter, digit, and punctuation codes used by this converter. https://www.itu.int/rec/R-REC-M.1677/en
• International Radiotelegraph Convention, Berlin, 1906, the treaty that adopted SOS as the international distress signal.
• American Radio Relay League (ARRL), Morse code proficiency resources, https://www.arrl.org/morse-code
• Radio Society of Great Britain (RSGB), Morse training, https://rsgb.org/main/operating/licensing/morse/
• Wikipedia, Morse code, historical and technical background on the Paris 1865 timing standard, https://en.wikipedia.org/wiki/Morse_code

Frequently Asked Questions

What does SOS actually mean? SOS is the international Morse distress signal, with the pattern ... --- .... The letters S, O, and S were chosen because they are easy to send accurately under stress, three short, three long, three short, but the meaning of SOS is "distress", not "save our ship" or "save our souls". SOS is itself the signal, not an abbreviation of anything. It was adopted at the 1906 International Radiotelegraph Convention in Berlin and is still recognised worldwide.

Why is the standard speed fifteen words per minute? Fifteen words per minute was the most common operational speed for trained commercial and military telegraphers in the twentieth century, fast enough to be useful but slow enough that almost anyone with a few weeks of training could copy at it. The "PARIS" word used to define the words-per-minute metric contains all the timing elements of Morse and is fifty dits long, so one word per minute equals fifty dits per minute and fifteen words per minute equals 1200 ÷ 15 = 80 milliseconds per dit.

Can I send accented characters? No, not in standard International Morse. The ITU-R M.1677-1 table covers only the 26 letters of the unaccented Latin alphabet, the 10 digits, and a small set of punctuation marks. If you need to send accented characters or non-Latin scripts, you must first transliterate them. The encoder in this tool will replace any character outside the table with a ? so you can see where the gap occurred.

Why are some letters shorter than others? Letters that occur more frequently in English (E, T, A, O, I, N) have shorter Morse codes than rarer letters (Q, J, Y, X, Z). This is the same trick Vail used in the original 1840s code: shorter codes for common letters speed up transmission. The trade-off is that the longer letters take more time, but on average the common ones save more time than the rarer ones cost.

What is the difference between standard spacing and continuous form? Standard spacing uses a slash surrounded by spaces between words (.... . .-.. .-.. --- / .-- --- .-. .-.. -..). Continuous form strips those slashes and runs all the dots and dashes together with single spaces (.... . .-.. .-.. --- .-- --- .-. .-.. -..). The decoder accepts either form. The audio scheduler produces the same sound in both cases because it infers word boundaries from the longer inter-word silence in the encoded stream.

Is Morse code still taught? Yes. The American Radio Relay League (ARRL) runs Morse proficiency courses at most of its conventions. The Radio Society of Great Britain (RSGB) and the Deutscher Amateur-Radio-Club (DARC) do the same. Several national militaries still teach Morse as part of signals training. Morse is also taught in many schools as a STEM outreach activity because it exercises both language skills and pattern recognition.

How does this converter differ from a physical Morse key? A physical Morse key is a single-pole single-throw switch that the operator opens and closes by hand. The skill of operating a key well is its own art form, with a target speed of fifteen to twenty-five words per minute and a target timing accuracy of a few percent. This converter skips the mechanical part entirely: the encoder produces a perfect timing pattern on the first try, the decoder accepts any pattern, and the audio scheduler plays back the chosen pattern at the chosen speed. It is the same code, but with all of the manual skill factored out.

Is there a way to listen to my own text? Yes. Type or paste any text into the top textarea, choose a speed with the slider (5 to 25 wpm), choose a pitch with the pitch slider (300 to 900 Hz), and press Play. The Web Audio API schedules a sine-wave tone for each dit and dah with the correct Paris-standard gaps between characters and words. The Stop button halts playback immediately.