Fast v2: many tones at once, up to about 150 bits a second, with error correction. Both devices need this version of the page; a classic v1 receiver cannot read it (and the other way round).

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Sound options

The WAV is the same message sound the Play button makes (saved at 44.1 kHz). To send it over a call or as a voice note, play it into the phone’s microphone or share the file; voice apps squash audio, so Classic mode survives that better than Fast, and near-ultrasonic does not survive it at all.

Open this page on two devices — one on Send, one on Receive. Turn the volume up, keep them close, and it works best in a quiet room. Sound can be heard by anyone nearby.

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Nothing is uploaded. Just open it and start.

Send text between devices using sound

Free, no sign-up, no credit card, no trial. No pairing and no network — type a message on one device and it plays as a burst of tones with error correction; open this page on a second device, tap Receive, and it listens through the microphone and turns the tones back into text, a link, Wi-Fi details or a contact.

Fast and classic modes

Fast plays many tones at once, about 6 times quicker than classic on long texts; classic keeps the slow single-tone sound as a fallback.

Verified or flagged

Error correction repairs damaged tones; if it can't, you are told to ask for a replay instead of seeing wrong text.

Live level meter

A level and spectrum meter says when the room is too noisy or the sound too quiet, and decoding runs off the main thread.

No network needed

Text, links, Wi-Fi and contacts, plus save as WAV and a local history. Nothing is uploaded.

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Frequently asked questions

How does sending data by sound work?
Your message is turned into bytes, packed with error-correcting codes, and played as tones, a simple audio modem. The other device listens through its microphone, finds the start of the message, reads the tones and rebuilds the bytes. No internet, Bluetooth or pairing is involved: just sound in the air.
What is the difference between Fast (v2) and Classic (v1)?
Fast v2 plays four tones at once and reads them by timing, giving about 150 bits a second of message on longer texts (a short message is mostly start-up and error-correction bytes), with a checksum and Reed-Solomon error correction. Classic v1 plays one tone at a time at about 3 bytes a second with a simple checksum and plain text only. The two sound different and carry a different start marker, so a receiver always says which one it heard and one never decodes the other as garbage. Both devices need this version of the page.
What does Received (verified) mean?
A fast v2 message is shown as verified only when every error-corrected block decodes and the CRC-16 checksum of the whole message matches. Up to a few damaged tones are repaired automatically, and the page tells you how many. If it can't be repaired you see Corrupted, ask the sender to replay, instead of altered text. A classic v1 message only has a small 8-bit checksum, so it is labelled basic check passed.
What does Send twice do?
The sender plays the message two times with a pause between. Both copies carry the same message id, so the receiver shows one message, keeps whichever copy arrived intact, and tells you if two intact copies somehow disagreed.
What can I send besides text?
Links, Wi-Fi details and contacts. Wi-Fi and contacts use the same text formats as QR codes. Links are shown with their host name and only open when you click. Wi-Fi passwords are hidden until you press Show and are never saved to the history. Longer text is compressed with a small built-in compressor when that makes it shorter, and the counter shows bytes, not characters.
What is near-ultrasonic mode?
Fast mode can use tones around 16.5 to 19.7 kHz, which most adults barely hear. Many phone and laptop speakers and microphones cannot play or pick up sound that high, and phone calls, voice notes and Bluetooth remove it, so it often fails. The receiver must tick Listen for near-ultrasonic, and its microphone needs a sample rate of at least 40 kHz. Children and pets may still hear a faint whistle.
Does it work in a background tab?
Decoding runs in a Web Worker, so a receiving tab that is hidden keeps decoding while it is open and the microphone stays on. If the browser can't start a worker the page decodes on the main page instead and says so. Some phones still pause audio when the screen locks; the page tells you if the browser paused it.
Can I send it over a phone call or voice note?
Save as WAV makes the same message sound the Play button plays (rendered at 44.1 kHz). Voice apps compress audio hard, so Classic mode has the best chance, Fast may fail and near-ultrasonic will not survive. Playing the file next to the other phone's microphone is more reliable than a call.
Is it secure or private?
Everything happens on your devices and nothing is uploaded. The microphone only turns on when you press Start listening and is switched off when you press Stop or leave the page. But sound travels through the air: anyone nearby, or any recording, can get the message. Do not use it for secrets. The received-messages list stays in this browser, holds at most 30 entries and can be deleted.
Why is there a size limit?
Fast mode carries up to 1,024 bytes of what you type (compression can make it shorter on the air) and a full message takes about a minute; Classic is limited to 64 characters. Longer messages take longer and have more chances to be damaged.

Spotted a bug or have a suggestion?

Found something broken, have an idea, or just want to say thanks about any of our tools? Every message reaches a real person.