Morse Code Audio Decoder
Listen to a tone through your microphone, or tap out a signal by hand, and watch it turn into text as you send it — timed against the same dot-dash-and-gap ratios a real Morse operator uses.
Decoder
How the Audio Decoder Works
The decoder measures how long a tone stays on and how long the silence lasts between tones, then compares those durations against each other. International Morse Code defines a dash as three times the length of a dot, a gap between the dots and dashes of one letter as one dot-length, a gap between letters as three dot-lengths, and a gap between words as seven dot-lengths. Every character you send is judged against those ratios, not a fixed speed.
Because the ratios matter more than the absolute speed, the decoder learns your dot length as you go: the first short pulse sets an initial estimate, and every pulse it classifies as a dot afterward refines that estimate. This is the same adaptive-timing approach real software decoders use, and it’s why sending at a consistent, steady pace matters more than sending fast.
In microphone mode, the decoder reads your device’s audio input roughly sixty times a second and treats any moment louder than the sensitivity threshold as a tone. In Tap Key mode, the same logic runs on how long you hold the button or the spacebar down — there’s no separate decoding engine for the two, only a different source for when a “tone” starts and stops.
Tips for Reliable Decoding
Use a quiet room. Background noise — a fan, traffic, conversation — can register as tone and break up your signal. A quiet space gives the sensitivity slider more room to work with.
Keep the tone source close and consistent. If you’re playing a tone from another device, keep it a fixed distance from the microphone. Moving it changes the volume mid-signal, which can make a dot register as silence or a dash as two dots.
Send at a steady, unhurried pace. The decoder calibrates to your speed, but only if your dots stay roughly the same length as each other. Rushing the first few characters throws off the calibration for the rest of the word.
Adjust the sensitivity slider if needed. If the decoder is missing quiet tones, raise the sensitivity. If it’s picking up background noise as tone, lower it. The meter bar shows what the decoder is currently hearing, which makes it easier to find the right setting.
If you’d rather build recognition speed than send your own signal, the Morse Code Practice & Quiz trains you to read patterns instead of send them.
Frequently Asked Questions
Do I need a real Morse key to use this?
No. Tap Key mode works with a mouse click, a touchscreen tap, or the spacebar — anything you can hold down for a short or long press. Microphone mode works with any audible tone: a whistle, a beep from another app, or an actual telegraph key wired to a speaker.
Why isn’t my microphone picking up the signal?
Check that your browser has been given microphone permission for this site first. After that, the most common causes are the tone source being too quiet or too far from the microphone, or the sensitivity slider being set too low. The level meter shows exactly what the decoder is hearing in real time, which makes it easy to tell which one applies.
Can it decode a recorded audio file instead of live sound?
Not currently — this tool listens to live microphone input only, it doesn’t accept file uploads. If you want to convert typed text or a written-out pattern instead, the Morse Code Translator handles that instantly.
How is this different from the Morse Code Translator?
The Translator converts typed text and Morse code back and forth instantly, with no timing involved. This decoder listens to an actual tone’s on/off timing — through a microphone or a tap — and reconstructs the message from how long each part was held, the way a person reading real Morse code by ear has to.