What is altcoin?

Any cryptocurrency other than Bitcoin.

The term is informal and covers everything from Ethereum to obscure tokens, so it says little about an asset's size or legitimacy.

It survives because it is convenient, not because it is precise. A word that groups a network settling billions of dollars a day with a token launched an hour ago is doing no analytical work. When someone says altcoins are up or down, they usually mean a specific index of large assets, and they rarely say which.

How it works

The category is defined by exclusion, so its only shared property is not being Bitcoin. Inside it sit at least four things with almost nothing in common.

Independent layer 1 networks, such as Ethereum and Solana, run their own consensus and their own security budget. Their native coin pays for block space, which gives it a use inside the system.

Tokens issued on top of another chain, such as an erc 20 on Ethereum, borrow that chain's security and pay its fees. Issuing one requires deploying a contract, which anyone can do for the cost of a transaction. This is why the count of existing tokens is in the millions and tells you nothing.

Stablecoins are technically altcoins and behave nothing like the rest of the category, being designed not to move in price at all.

Forks of Bitcoin's codebase, such as Litecoin and Bitcoin Cash, are altcoins by the definition despite sharing most of Bitcoin's design.

Example

Illustrative: two assets are both described as altcoins. One has a $40 billion market value, trades on 20 regulated venues, and shows a 0.02% spread on a $50,000 order. The other has a $4 million market value, trades on two venues, and a $50,000 order moves the price 18%. Both are in the same category and the second is not sellable at anything near its quoted price. The category told you nothing; the depth measurement told you everything.

Why it matters when you buy

Because the label is empty, the questions you actually need answered are venue coverage, order-book depth, and supply concentration, all of which vary by orders of magnitude inside the category. Check where an asset is listed at the buyability scores, how deep the book is at the liquidity pages, and how tightly the supply is held at the concentration view.

Related terms

• market cap — price times circulating supply, not price alone
• token — an asset issued on another chain
• memecoin — the thinnest end of the category
• erc 20 — the standard most tokens use
• delisting — how thin assets leave venues
• fdv — valuation including supply not yet issued

Questions

Is Ethereum an altcoin?

By the literal definition, yes, though many people now treat it as its own category given its size and role. The disagreement is about usage, not about any property of the asset.

Do altcoins move together?

They correlate strongly during sharp moves, and much less at other times. Correlation is a measured relationship that changes, not a rule you can rely on.

Why do some exchanges list thousands of altcoins and others a few dozen?

Listing standards and licensing differ. Venues operating under strict regimes list assets that survive a legal and liquidity review, while venues in lighter jurisdictions list far more. See the exchange directory for what each venue offers.