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Runes: Fungible Tokens on Bitcoin

Bitcoin Advancedadvanced6 min read
Casey Rodarmor's second protocol. Why Runes replaced BRC-20 as the leading Bitcoin token standard and how it fits the UTXO model.

Runes launched at the April 2024 Bitcoin halving. Same author as Ordinals (Casey Rodarmor), different design goal: a fungible token standard that fits Bitcoin's UTXO model natively and does not require indexer trust the way BRC-20 does.

Why Runes over BRC-20

BRC-20 uses Ordinals inscriptions to declare balances. Each transfer requires a new inscription. This means every wallet needs an off-chain indexer to know balances. It works but it is slow, inefficient, and depends on trusted indexers.

Runes design

Runes writes token operations directly into the OP_RETURN of Bitcoin transactions. Balances live in UTXOs, exactly like BTC. A UTXO can hold both BTC and some quantity of a Rune. When you spend the UTXO, the Rune moves too.

What Runes enables

Launch mania

The Runes launch on halving day (April 20, 2024) created a fee spike that briefly pushed the average Bitcoin transaction fee above $100. Some Runes minted at halving-block priority commanded thousands of dollars in fees per mint. The market normalized within weeks.

Where Runes fits

Trade-offs

PreviousBitcoin Ordinals and Inscriptions NextBRC-20: How Fungibles Started on Bitcoin
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