Bitcoin

Bitcoin is a digital asset that exists as entries on a public, shared ledger called the Bitcoin blockchain. Transactions are broadcast to a network of participants, grouped into blocks and recorded, so the ledger holds a complete history of every transfer. There is no company, no board and no central administrator. New bitcoin comes into existence as a reward paid to whoever adds a valid block, a process called mining, and the value of a bitcoin is set by what buyers and sellers will pay rather than by any issuer's promise.

Bitcoin is one instance of the broader cryptocurrency category, and most of what is true of digital assets generally is true here: it is treated as property rather than currency for federal tax purposes, it carries no deposit insurance, and its regulatory classification is contested. What makes it worth a page of its own is that it was first, that its supply schedule is a checkable property of the software rather than a policy decision, and that it is the asset against which the rest of the market is measured.

The supply schedule is the design feature everything else is built around, and the honest version of it is more interesting than the slogan. An exchange filing published in the Federal Register describes the mechanism this way: under the source code that governs the network, the supply of new bitcoin is mathematically controlled so that it grows at a limited rate on a pre-set schedule, and the number of bitcoin awarded for solving a new block is automatically halved after every 210,000 blocks, approximately every four years. That controlled rate means the number in existence increases until it reaches the pre-determined 21 million.

The same filing then adds a qualification that the shorthand version of the story drops. The 21 million supply cap could be changed in a hard fork, because a hard fork could change the source code of the network, including the cap itself. The limit is therefore a rule the participants currently agree to enforce rather than a physical constraint. Whether that distinction ever matters in practice is a question nobody can answer, but a reader deciding how much weight to put on scarcity should know which kind of scarcity it is.

What bitcoin is not is worth stating as carefully as what it is. It is not issued by a central bank and, as FINRA notes of native crypto assets generally, it is not designated as legal tender by governments outside a handful of smaller countries. It produces no cash flow, so the tools used to value a bond or a share, discounting future payments, have nothing to work on here. Its price is determined by supply and demand on trading platforms and in private transfers, which is why filings describe its market dynamics as influenced by macroeconomic conditions, adoption and the regulatory environment rather than by anything analogous to earnings.

Its position in the market is the second thing that distinguishes it. In January 2024 the SEC approved exchange rule changes permitting the listing and trading of what its own order calls spot bitcoin exchange-traded products, under a listing category the order titles Bitcoin-Based Commodity-Based Trust Shares and Trust Units. That gave ordinary brokerage accounts a route to bitcoin exposure without direct custody, and bitcoin was the first digital asset to have it. Listed spot products on other digital assets, including ether and solana, have since followed, so this is a matter of being first rather than of being alone. Bitcoin remains the reference asset the rest of the market quotes itself against, in the way a benchmark index functions in equities.

Decentralization is a matter of degree rather than a binary, and the filing language is careful about it: the network is "commonly understood to be decentralized" and does not require governmental authorities or financial intermediaries to create, transmit or determine value. That is a description of the protocol. It says nothing about the concentration of mining capacity, of holdings, or of the platforms most people actually trade through, all of which are separate questions a buyer may care about more.

Transactions are broadcast to the network and gathered into blocks. Miners compete to add the next block, and the winner receives newly created bitcoin plus the fees attached to the transactions in that block. Each new block records outstanding transactions, so the chain of blocks is a running record of every transfer that has settled. Ownership rests on control of a cryptographic key rather than on an account at an institution, which is why the practical question for an owner is where the keys live rather than which firm holds the balance.

The halving is the schedule that governs new issuance, and it is arithmetic rather than discretion. The block reward is cut in half every 210,000 blocks, which at the network's target pace works out to roughly four years, and this continues until issuance reaches the 21 million limit. Nothing about the halving is announced or voted on; it happens because the software says so at a particular block height. The mechanics and history of past halvings are enough of a subject to sit on their own page.

For a household, there are three practical routes to exposure, and they differ in what you own and who can lose it for you. Buying and holding on a platform means the platform holds the keys and you hold a claim against it. Self-custody in a wallet you control removes that counterparty and hands you the entire responsibility, with no password reset available. A spot bitcoin exchange-traded product is a listed security bought in an ordinary brokerage account, where the fund holds the asset and you hold shares in the fund. Each route has a different failure mode, and choosing between them is mostly a question of which failure you would rather be exposed to.

What is genuinely distinctive

• The issuance schedule is fixed in software and publicly checkable, which is unusual among assets and is the property most buyers are actually buying.
• There is no issuer to default, no board to dilute holders, and no jurisdiction whose permission is needed to transfer it.
• Its size and history mean it has deeper trading markets and more regulated access routes than other digital assets, including listed spot products.
• Self-custody is genuinely possible, so ownership need not depend on any institution remaining solvent.

What a buyer is accepting

• No cash flow at all, so there is nothing to value it against and price rests entirely on what the next buyer will pay.
• FINRA describes crypto assets generally as often exceptionally risky and volatile, with a significant risk of losing the whole investment.
• The 21 million cap is enforced by the software and by the network's agreement to keep running it, and exchange filings state that a hard fork could change it.
• Direct custody is unforgiving. A lost key generally means the asset is gone, and recovery after theft is rare.
• It is not legal tender in the United States and is treated as property for tax, so spending it is a disposal that creates a gain or loss.