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Fine tuning
Leave Tone and Speed empty and the decoder finds them itself. Set them only if the result looks wrong, for example a single repeated letter that has no gaps to learn from.
Everything happens in your browser. Your audio is not uploaded anywhere.
A Morse code audio decoder turns beeps into letters. Choose an audio file or press Record, and the decoder finds the pitch of the beeps, measures how long each one lasts and prints the message. It runs in your browser, so your audio is never uploaded.
How to decode Morse code from audio
- Add the sound. Choose a file (WAV, MP3, M4A, OGG or WebM), drop one onto the box, or press Record with microphone and play the Morse code near it.
- Wait a moment. The decoder finds the pitch that repeats in short and long bursts, then works out the speed from the lengths of the bursts.
- Read the result. The decoded text and the Morse code it heard appear side by side. The spectrogram shows the pitch as a bright bar, so you can check that it found the right signal.
- Adjust if needed. Open Fine tuning to change the sensitivity, or to type the pitch or speed if you know them.
Not sure what to try? Press Try an example to decode a sample message with background noise.
How it works
Morse code audio is a single steady tone switched on and off. The decoder does this:
- Finds the tone. It scans the spectrum for a narrow peak and ignores broad noise such as hiss or a hum.
- Follows the loudness at that pitch. The level rises for each beep and falls in each gap.
- Measures the beeps. Short beeps are dots and beeps about three times longer are dashes. The decoder learns the dot length from your recording instead of assuming a speed.
- Reads the gaps. A gap about as long as a dot separates the parts of a letter, a longer gap separates letters and the longest separates words. It copes with slow "Farnsworth" spacing, where the gaps are stretched but the beeps stay fast.
The approach is similar in principle to the software decoders radio amateurs use, and it is tested here on generated audio at speeds from 8 to 35 words per minute and pitches from 400 to 900 Hz, with noise and uneven hand timing added.
What works well and what does not
Works well
- Clean recordings of a single tone, such as practice files, game audio and generated beeps.
- Radio recordings where the signal is clearly louder than the noise.
- Hand-keyed Morse code with natural, uneven timing.
Does not work well
- Several signals at once. Two stations on different pitches in the same recording confuse a decoder that listens for one tone. Filter the recording or cut it first.
- Very noisy audio. If the beeps drown in static, the decoder says so instead of guessing.
- Speech or music over the top. Voices and instruments have no steady tone to lock onto.
- Single letters. One E or T gives the decoder nothing to compare against. Type the speed in Fine tuning if you need it.
When the result looks wrong, try the Sensitivity slider first. Then check the spectrogram: if the bar sits at a different pitch from the one shown in the result, type the correct pitch into Fine tuning.
Using the microphone
Press Record with microphone, allow access when your browser asks, then play the Morse code or send it with a key or buzzer. Press Stop and decode when it ends. While you record, the page shows a live reading of the last 40 seconds. Your browser asks for permission each time unless you choose to remember it, and recording stops when you leave the page.
Hold the sound source close to the microphone and keep the room quiet. If you use headphones, the microphone will not hear them. Play the audio through a speaker instead.
Frequently asked questions
How do I translate Morse code audio to text?
Add the audio with the file box or the microphone button. The decoder finds the beeps, measures them and writes the text. You can copy it or open the Morse code in the main translator.
What audio formats are supported?
Whatever your browser can open, which normally includes WAV, MP3, M4A, OGG and WebM. Files longer than three minutes are cut to the first three minutes.
Can it decode Morse code from a video or a phone call?
If you can play the sound near the microphone or save it as an audio file, yes. For a video of a blinking light, use the image and light reader instead.
Why does it show a speed I did not expect?
The decoder reports the speed it measured in words per minute, using the standard word PARIS. Hand-keyed code is rarely perfectly steady, so the number is an average.
Is my audio uploaded?
No. The file is decoded by your browser. Microphone recordings stay in the page and are discarded when you leave it.
Decipher Morse code audio
To decipher Morse code audio, upload a recording or use the microphone. The decoder picks out the tone, works out the speed and writes the text. It works best with a clear tone, such as an SDR or radio recording with the signal tuned in, a beeping alarm or a game sound. If your recording is very noisy, the decoder says so rather than guessing. It runs privately in your browser, but it will not beat a trained ear on a very weak signal. To use your computer's microphone as the source, press the microphone button.