Altcoin Season Index

How it works

The Altcoin Season Index answers one question: of the largest coins, how many have done better than Bitcoin recently? CoinMarketCap publishes it daily and describes the method:

• The basket: the top 100 coins by CoinMarketCap ranking at the end of each day, excluding stablecoins (such as USDT and DAI) and asset-backed or wrapped tokens (such as WBTC and stETH). Ethereum counts as an altcoin.
• The comparison: each coin's rolling 90-day price change against Bitcoin's 90-day price change.
• The score: the share of the basket that outperformed Bitcoin, scaled to a 1–100 number. It reads roughly as "how many of the 100 beat Bitcoin".

CoinMarketCap's thresholds give the labels:

Two details shape how the number behaves. The 90-day window makes it slow: a new move has to last weeks before it shifts the score much. And the basket is not fixed. Coins enter and leave the top 100 every day, so a reading from two years ago compared Bitcoin against a different group of coins than today's.

A worked example

Over the last 90 days Bitcoin rose 12%. Count the top 100 coins (after exclusions) that rose more than 12%.

Case 1: a mixed market. 38 coins beat Bitcoin. The index reads about 38, neutral.

Case 2: everything up, index at the bottom. Every altcoin rose 11%, one point less than Bitcoin. None beat it, so the index sits near its floor, Bitcoin season, although every coin in the basket gained 11%.

Case 3: everything down, index at the top. Now take a falling market: Bitcoin fell 30% over 90 days and 80 coins fell less, say 25%. Those 80 count as outperforming, and the index reads about 80, altcoin season, while all of them lost a quarter of their value.

The index counts winners against Bitcoin. It says nothing about whether anyone made money, or by how much the winners won. One coin that tripled and one that beat Bitcoin by 0.1 percentage points count the same.

What it tells you

The box above shows CoinMarketCap's latest reading and its range over the past 90 days. Because the score is built from 90-day returns, the sparkline moves in broad waves. It rarely jumps from Bitcoin season to altcoin season in days, and a change of label usually confirms a shift that started weeks earlier.

A high reading means outperformance is broad: most large coins are beating Bitcoin, which has historically gone with risk-seeking phases of the market, when money moves out along the curve from Bitcoin to Ethereum, then to large caps and smaller tokens. A low reading means Bitcoin is leading and the market is more defensive.

The index is closely related to Bitcoin dominance, but the two are not the same:

When altcoins as a group beat Bitcoin, dominance usually falls at the same time. They can diverge: Ethereum alone outperforming moves dominance a lot and the index by one coin, while many small coins outperforming moves the index a lot and dominance very little.

When it matters most

The reading carries the most weight when it agrees with dominance. A rising index together with falling dominance and rising total market cap describes a broad rotation into altcoins. A high index with flat dominance usually means many smaller coins outperformed while the largest altcoins did not.

It is least useful right after a sharp move. A fast rotation in either direction takes weeks to show up, because most of the 90-day window still reflects the period before. Late in a strong altcoin run, the index can still be rising while the move is already reversing.

It also matters which coins are doing the outperforming. A high reading can come from broad strength across sectors, or from one narrative lifting many related tokens at once. The index cannot tell the two apart. SwapHunt reads it next to the Fear and Greed Index and the market regime for that reason.

Common misconceptions

"Altcoin season means altcoins are going up." It means most large altcoins are beating Bitcoin. In a falling market that can simply mean they are falling less, as case 3 shows.

"The index reacts to what is happening now." It compares 90-day returns. A rotation that started last week barely registers yet.

"The index compares the same coins over time." The top 100 is rebuilt every day. Readings years apart describe different baskets, so historical comparisons are looser than the single number suggests.

"A higher score means bigger gains." The index counts how many coins beat Bitcoin, not by how much. A score of 80 can come from 80 coins that each beat Bitcoin by a fraction of a percent.