How to write a message into the Bitcoin blockchain

• What OP_RETURN is
• How much fits in
• A tradition as old as Bitcoin
• Public and permanent
• What it proves, and what it doesn’t
• Don’t trust, verify

Bitcoin is mostly used to move value, but every transaction can also carry a short piece of text. People have used it for years to record a birth, a wedding or the memory of someone they lost. Once the transaction is in a block, anyone can read the text, nobody can change it, and it doesn’t depend on any company staying in business.

§What OP_RETURN is

An OP_RETURN output sends no coins and can never be spent. Its only job is to carry a small amount of data. Because it is provably unspendable, it never enters the UTXO set that every full node keeps. The data sits in the block, and that’s it.

§How much fits in

The standard limit is 80 bytes. Bytes are not characters: plain letters take 1 byte, letters with diacritics 2, most emoji 4. In practice, one or two short sentences.

A Timestone message starts with a 5-byte format tag, which leaves 75 bytes for the text:

TS1B:Welcome to the world, Ema! Born 4 Oct 2026

§A tradition as old as Bitcoin

The genesis block from January 2009 carries the line “The Times 03/Jan/2009 Chancellor on brink of second bailout for banks”. A life-event message follows the same idea: one short, meaningful line, an ordinary network fee, the smallest standard format. No images, no files, no inscriptions.

§Public and permanent

• Anyone can read it.
• Nobody can delete or correct it, including you.
• Use first names, initials or nicknames, especially for children. Never full names or addresses.

§What it proves, and what it doesn’t

A message in a block proves the text existed in this exact form no later than that block, and that it hasn’t changed since. It doesn’t prove the event happened, or when. And it is not a legal document.

§Don’t trust, verify

You don’t need Timestone to read a message. Open the transaction in any explorer, such as mempool.space, and find the OP_RETURN output.

The full article covers how to write a message by hand, in a wallet, or with Timestone, where you sign with your own wallet and nobody else holds your keys:
https://timestone.app/blog/write-a-message-into-the-bitcoin-blockchain?utm_source=nostr&utm_medium=social&utm_campaign=blog-op-return