Send text between devices using sound

Frequently asked questions

How does sending text by sound work?

Your text is turned into a sequence of short musical tones — a simple audio modem. Each pair of tones encodes one byte of your message, wrapped in start and end markers. The other device listens through its microphone, works out which tone is playing from moment to moment, and reassembles the original text. No internet, Bluetooth, or pairing is involved — just sound in the air.

What do I need to make it work?

Two devices, both with this page open — one set to Send and one to Receive. Turn the volume up on the sender, allow microphone access on the receiver, keep them close together, and it works best in a quiet room. You can also test it with two browser tabs on the same computer.

How reliable is it?

It's a fun demo rather than a robust file-transfer tool. Background noise, echoey rooms, low volume, or distance between the devices can garble the message. Short messages in a quiet room, with the devices close and the volume up, decode most reliably.

Is it secure or private?

Everything happens on your devices — nothing is uploaded. But sound travels through the air, so anyone (or any microphone) nearby could hear the tones. Don't use it for secrets; treat it like speaking the message aloud.

Why is there a length limit?

Each character takes a fraction of a second to play as tones, so longer messages take longer to send and are more likely to pick up an error along the way. Keeping messages short keeps them quick and reliable.