What is Runes?

A fungible token protocol for Bitcoin that records balances in transaction outputs rather than in inscriptions, launched at the fourth halving in April 2024.

Runes was designed by the author of ordinals as a leaner alternative to brc 20, storing its data in a single output that non-participating wallets can ignore (source: the ord project documentation). Balances live in the utxo set, so a Runes transfer is a normal Bitcoin transaction to a node that does not know the protocol.

The design goal was to stop token activity from bloating the utxo set the way earlier schemes did. Whether that succeeded is a matter of debate among Bitcoin developers. What is not debatable is the practical situation for holders, which is that exchange support is thin and mistakes are unrecoverable.

How it works

1. Balances attach to outputs. A Rune balance is associated with a specific unspent output rather than with an address. Spending that output moves the balance.
2. A single data output carries instructions. Protocol messages are encoded in one output that Bitcoin nodes treat as unspendable data, so nodes that do not implement Runes simply ignore it (source: the ord project documentation).
3. Etching creates a Rune. A one-time transaction defines the name, supply, and divisibility.
4. Minting and transfer follow standard transactions. Any wallet-aware software constructs the outputs; the Bitcoin network validates them as ordinary transactions.
5. Bitcoin itself does not enforce token rules. Validity is determined by Runes-aware software reading the chain, not by consensus.

That last point is the crucial one. To Bitcoin, a Runes transfer is just a transaction. If a wallet that does not understand Runes spends the output carrying a balance, Bitcoin considers the transaction perfectly valid and the token balance is gone.

Example

Illustrative and common. You hold a Rune balance in a compatible wallet. You then send some Bitcoin using a different wallet, or the same wallet in a non-aware mode, and its coin selection happens to spend the output carrying the Rune balance as an ordinary input.

The Bitcoin transaction succeeds. The Rune balance is destroyed or transferred to whoever received that output, and there is no error message, because nothing invalid happened. The same failure occurs when a Rune is sent to an exchange deposit address that does not support the protocol: the Bitcoin arrives, the Rune does not, and support cannot recover it.

This is why coin control matters for anyone holding these balances.

Why it matters when you buy

Support is the whole story. Most exchanges do not credit Runes deposits, and sending one to an exchange address will usually lose it permanently. Before acquiring any, confirm your wallet is protocol-aware and confirm what your exchange actually supports rather than assuming Bitcoin support covers it. Buyability and the exchange directory cover availability.

Related terms

ordinals — the inscription protocol by the same author; brc 20 — the earlier token scheme; utxo — where balances actually live; coin control — choosing which outputs to spend; dust — small outputs that carry balances; token — the general category.

Questions

Can I store Runes in any Bitcoin wallet?

Only in one that understands the protocol. A standard wallet will show the Bitcoin and may spend the output carrying the token balance without warning, destroying it.

Do exchanges support Runes?

Few do. Bitcoin support does not imply Runes support, and deposits sent to a non-supporting address are lost. Confirm on the exchange's own asset list before sending anything.

How is this different from BRC-20?

BRC-20 records balances in inscriptions and creates more chain footprint per operation. Runes records balances in outputs with a single data field, which was the design goal, though both remain far less supported than tokens on general-purpose smart contract chains.