satwire
live API

Write a message on the Bitcoin blockchain

Permanently, in an OP_RETURN output. Pay with Lightning or on-chain.

sats
Optional. SatWire publishes your message — this only adds a payment on top.
0
slower faster

On the wire

18 published

Welcome to the world, Gabriel! 8 October 2026 I hope you have an amazing life, I can’t wait to see who you become! -Morbror Carl

Leonardo e Caterina, Mimì e Hopi 04-09-2020 insieme per sempre nell'amore.

hey jeet, it looks like you’ve come into some unexpected money. I find out where you stay. Could you please send 6 BTC to this address by 2026/09/30. bc1qhx8fee4wpg3uzsmxtnfp9cvczmns0x7me5lwt9

Hello Future! I hope this network will serve you well and will allow people to agree on this common ground for value exchange and come together. Satoshi Nakamoto's invention, this Bitcoin Network, has made wealth an immaterial matter, which can live in our heads and is much more difficult to expropriate. This will change how organizations of people work.

Blocktrainer Forum : https://forum.blocktrainer.de/invites/AyhecyHyag

Hallo ich bin Stuart Deari und ich studiere Rechtswissenschaften an der Uni Wien

What SatWire does

SatWire writes your message into the Bitcoin blockchain itself. Not a link to it, not a hash of it — the text, in an OP_RETURN output of a real Bitcoin transaction, where it stays as long as Bitcoin does. You get the transaction id and can check it in any block explorer.

There is no account and no signup. You type a message, we quote a price, you pay — a Lightning invoice, or a one-off Bitcoin address — and the transaction is broadcast. You can publish a picture the same way: it is resized and re-encoded to WebP in your own browser, so the original file never leaves your device and its GPS data never goes anywhere. The bytes that reach the chain are a complete, valid image file — anyone can pull them out of the transaction and open them, with no tool of ours.

New to this? What OP_RETURN is, how many bytes fit, and how the price is worked out →

What it costs

Two parts: a flat 3,000-sat service fee, and the Bitcoin network fee for the transaction. The network fee depends on how big your message is and how fast you want it confirmed — a short line of text costs about 440 sats to publish, a picture costs more because it is bigger.

Roughly, at the cheapest fee rate, service fee included
What you publishOn-chain sizeTotal
A line of text~100 bytes~3,440 sats
Picture, 160×120~1,500 bytes~6,250 sats
Picture, 256×192~2,840 bytes~8,930 sats
Picture, 512×384~7,880 bytes~19,000 sats
Picture, 1024×768~20,000 bytes~43,250 sats

The limits are 1,000 bytes for text and 20,000 bytes for a picture. The composer above shows the exact price before you pay anything.

Paying with Lightning costs the same two parts, a few sats more for the treasury's safety margin, and you skip the on-chain fee your own wallet charges to send a payment. Your message goes out within seconds of paying.

How it works

  1. Write your message, or attach a picture and pick a budget.
  2. You get an exact amount, and a Lightning invoice or a Bitcoin address to pay it to.
  3. You pay it. Nothing else is required of you.
  4. SatWire builds a transaction carrying your bytes and broadcasts it.
  5. You get the transaction id, and the message is on the chain forever.

Aiming a message at somebody else's address — a wallet, a stash, a counterparty? How that works, and whether they will see it →

Questions

Can anyone read what I publish?
Yes. The Bitcoin blockchain is public, and so is everything written into it. Do not publish anything you would not put on a billboard.
Can I delete it later?
No. Nobody can — not you, not us. That is the point of it, and the reason to think before you pay. Showing your message on the public wall here is a separate choice, and that one the operator can undo.
Can I pay with Lightning?
Yes. Choose Lightning next to the price and you get an invoice instead of an address. Pay it from any Lightning wallet: your message is published within seconds, and you skip the on-chain fee of sending a payment. An invoice is valid for 30 minutes.
Do I need an account or a wallet connection?
Neither. You pay from any wallet — a Lightning invoice, or a Bitcoin address we show you once.
How long does it take?
Over Lightning, the transaction is broadcast within seconds of paying. On-chain, it goes out once your payment has its first confirmation — about ten minutes on average. How long it then takes to be mined into a block depends on the fee rate you chose.
What if it cannot be published?
An on-chain payment is sent back to the address it came from, automatically. For a Lightning payment, your order asks for a Lightning address and the money goes back there. In the rare case neither works, the operator is alerted and sorts it out by hand.
Can other software read my picture, or only SatWire?
Any software. There is no wrapper and no format of our own — the data in the OP_RETURN is the image file itself, so a hex decode is enough.

Questions about OP_RETURN itself — how many bytes fit, whether it can be deleted, whether it is encrypted: read the explainer →

API

A small HTTP API for publishing to the Bitcoin blockchain without the composer. No key is needed for the public endpoints.

POST
/api/message-request Returns an address to pay. Body: message, and optionally targetAddress, amountToSend, feeRate, isPublic. Send paymentMethod: "lightning" for a Lightning invoice instead.
GET
/api/request-status/:idPoll a request.
DEL
/api/request/:idCancel, while unpaid.
GET
/api/wallMessages customers chose to show publicly.
GET
/api/payment-qr.svg?requestId=A BIP21 code for an open order.
POST
/api/internal/embedX-API-Key Publishes straight from the treasury. No payment step.
GET
/api/internal/treasuryX-API-KeyAddress and balance.