How to use the decoder
- Listen: press Listen, allow the microphone when the browser asks, and play the Morse code near your device. Press Stop and decode when it ends.
- Or upload: press Upload audio and choose a recording. Most WAV, MP3, OGG and M4A files work.
- Read the decoded text, the Morse code it heard and the speed. Copy either one.
- To check a result, paste the Morse into the Morse code translator and play it back.
Press Try an example to see a decode of a generated SOS HELP signal with a little noise added.
How it decodes the beeps
Morse code timing is built on one unit: a dot is one unit long, a dash three, the gap inside a letter one, the gap between letters three, and the gap between words seven. The decoder measures how loud the sound is every 5 milliseconds, splits it into tone and silence, and finds the dot length from the shortest beeps. Every beep and every gap is then sorted by length, and the result is read with the same table as the rest of the site.
Because it works from length alone, it adapts to any speed and any pitch, from a beeping app to a radio. It does need the beeps to stand out from the background.
Tips for a clean decode
- Get the microphone close to the speaker, and keep the room quiet.
- Trim long silences and talking from a file before you upload it.
- If letters run together, the sending speed is uneven. A recording of machine-sent Morse decodes best.
- For flashing-light Morse, write down the long and short flashes and type them into the Morse code translator.
Your audio stays on your device
The microphone is used only while you are listening. The recording, and any file you choose, is decoded by your browser and never uploaded or kept. See the privacy policy.
To learn to hear Morse yourself, try the Morse code trainer, and for the full table see the Morse code alphabet.