Bitcoin Ordinals Explained: How Sats Get Serial Numbers and NFTs

Bitcoin ordinals are a numbering system that gives every single satoshi its own serial number, so one specific sat can be tracked, and even carry data, as it moves from wallet to wallet. If you have seen people talk about "NFTs on Bitcoin," this is the idea underneath it.

That sounds odd at first. Bitcoin was built so that every coin is interchangeable with every other coin. Ordinals do not change that rule in the software. They are a way of reading the blockchain differently, and that small shift has had real effects on fees, wallets and a long running argument among Bitcoin developers.

How bitcoin ordinals number each satoshi

A satoshi is the smallest unit of bitcoin, one hundred millionth of a coin. (Our guide to what a satoshi is covers the basics.) Ordinal theory takes every sat ever mined and numbers it in the order it was created, starting with the first block.

When bitcoin moves, sats flow from a transaction's inputs to its outputs on a first in, first out basis, according to the Ordinals handbook. Because the order is predictable, anyone running the same software can follow a particular sat through every transaction it has ever been part of.

Think of a bank vault full of identical $1 bills. Every bill spends the same, but each one also has a printed serial number. Most people never look at it. Collectors do, and they will pay more for a bill with a rare serial. Ordinals add that serial number layer to Bitcoin.

The handbook is clear that this needs no extra token, no separate blockchain and no change to Bitcoin itself. Regular Bitcoin nodes do not know or care about ordinal numbers. Only software that follows ordinal theory, such as the open source `ord` tool, keeps track of them.

Rare sats

The scheme also labels some sats by rarity. The handbook lists six tiers: common, uncommon, rare, epic, legendary and mythic. The labels come from Bitcoin's schedule of blocks, halvings and difficulty changes, and some collectors trade sats based on them.

What an inscription adds

Numbering sats is only half the story. The part that made ordinals famous is inscriptions.

An inscription attaches content, such as an image, a text file or a small web page, to one specific sat. The handbook describes the result as "bitcoin-native digital artifacts, more commonly known as NFTs." Whoever holds that sat holds the inscription.

The content is stored entirely on the Bitcoin blockchain. Technically, it sits inside Taproot script data in the witness part of a transaction, which gets a discount in how Bitcoin measures block space. Creating one takes two transactions: a "commit" that sets up a Taproot output, then a "reveal" that publishes the content. Large files are split into pieces, because each data push is capped at 520 bytes.

The handbook's wallet guide gives a rough fee rule: divide the content size by four, then multiply by the fee rate. So bigger files cost more, and a busy network costs more still. An inscription transaction also has to stay under Bitcoin's standard size limit of 400,000 weight units.

Where you run into bitcoin ordinals

Most people meet ordinals in one of four places.

• Marketplaces and explorers. Inscriptions are bought and sold much like Ethereum NFTs. Ordinal explorers let you look up an inscription by number and see its content and history.
• Wallets. Not every Bitcoin wallet understands ordinals. A wallet that ignores them may spend the sat holding your inscription as part of a normal payment or fee. The `ord` project warns that Bitcoin Core "is not aware of inscriptions and does not perform sat control." (Our explainer on how crypto wallets work is a good primer on why this matters.)
• Fees. Inscriptions compete for the same block space as regular payments. A Crypto.com Research report from April 2024 counted about 63 million inscriptions, which had paid roughly 6,370 BTC in fees at the time. The same report said the weekly median fee hit 199 sat/vB in mid December 2023, a period heavy with inscription activity.
• Tokens. BRC-20 tokens were built on top of inscriptions in March 2023, per Crypto.com. Rodarmor later proposed Runes, a separate protocol for fungible tokens that stores its data in OP_RETURN outputs rather than inscriptions, as the Runes documentation explains.

The protocol was developed by Casey Rodarmor and went live on Bitcoin's main network in January 2023, according to Crypto.com. The handbook dates the finished numbering specification to early 2022.

Why some Bitcoin users dislike ordinals

Ordinals are popular, and also divisive. Critics see inscriptions as data that has nothing to do with payments, filling blocks and pushing up fees for people who just want to send money. Supporters reply that anyone who pays the fee is a valid user of block space, and that the extra fees help pay miners over the long term.

That debate spilled into Bitcoin Core itself. Version 30.0, released on October 10, 2025, raised the default `-datacarriersize` setting to 100,000 bytes, which the Bitcoin Core 30.0 release notes say "effectively uncaps the limit." It also allows several OP_RETURN outputs in one transaction. That change covers OP_RETURN data in general rather than inscriptions in particular, but it touches the same question of how much non payment data Bitcoin nodes should relay. Node operators can still set a lower limit.

Common myths about ordinals

"Ordinals are a new coin." They are not. There is no ordinal token. Inscriptions ride on ordinary sats, and BRC-20 and Runes tokens are separate layers built later.

"Ordinals required a Bitcoin fork." No fork happened. Ordinals rely on Taproot features that Bitcoin already supported.

"The image is stored somewhere else, like most NFTs." For inscriptions, the content lives on the Bitcoin blockchain itself. NFTs on other chains often store only a link to a file kept elsewhere.

"A rare sat or inscription always holds its value." Prices are set by collectors and can collapse. There is no guarantee anyone will buy what you hold.

"Any Bitcoin wallet will keep my inscription safe." As noted above, a wallet without sat control can send it away by accident.

Before you buy or mint an inscription

If you are just curious, an ordinals explorer is the easiest way to see inscriptions without spending anything.

If you plan to buy one, use a wallet that clearly supports ordinals and keep inscriptions in a separate wallet from the bitcoin you spend day to day. That one habit prevents the most common mistake, which is paying a fee with a sat you meant to keep. Treat unsolicited offers of "free mints" or airdrops with suspicion, since the usual crypto scam warning signs apply here too.

Before you mint or buy, check current network fees. A small inscription that looks cheap on a quiet weekend can cost far more during a busy stretch. For more plain English guides like this one, browse our crypto section.