What is the Altcoin Season Index?
The Altcoin Season Index measures whether altcoins are collectively outperforming Bitcoin over a rolling 90-day window. It compresses one question, whether capital is rotating out of Bitcoin and into the rest of the market, into a single number from 0 to 100.
A reading below 25 marks Bitcoin Season, where BTC leads returns and its share of total market value climbs. A reading above 75 marks Altcoin Season, where most large-cap altcoins, from Ethereum to Solana and XRP, are beating Bitcoin over the period. Everything in between sits in a neutral, transitional band.
The concept was popularised by Blockchain Center, and CoinMarketCap runs a widely cited version too. The live score, 7-day average and 30-day range shown above track where the market sits today.
How the Altcoin Season Index is Calculated
The score is built from the top 100 cryptocurrencies by market capitalisation, after removing stablecoins like USDT and wrapped or pegged tokens like WBTC. Each remaining coin's 90-day return is then measured against Bitcoin's over the same window.
The steps are simple:
- Pull the top 100 coins by market cap, then strip out stablecoins and asset-backed tokens.
- Calculate the 90-day price return for every coin and for Bitcoin.
- Count how many coins outperformed BTC across that window.
- Express that count as a percentage to set the final score from 0 to 100.
A score of 60 means 60 of the 100 coins beat Bitcoin over the past three months, and it refreshes daily. When you cross-check platforms, note the coin set: Datawallet and CoinMarketCap use the top 100, while the original Blockchain Center index uses the top 50, so the same day can read slightly differently even when the direction agrees.
How to Read the Current Score
The index sorts into three regimes:
- 0 to 25, Bitcoin Season: Capital concentrates in BTC, altcoins underperform, and Bitcoin dominance rises.
- 25 to 75, Neutral: A transition zone where selective names can run but no broad rotation is confirmed.
- 75 to 100, Altcoin Season: Risk appetite has spread outward and most large-caps are outpacing Bitcoin.
Through 2026 the index has stayed firmly in Bitcoin-led territory, reading in the 30s to mid-40s while Bitcoin dominance held near 58 to 60 percent. The last real push above 75 came in September 2025, when it touched the high 70s before retreating.
The trend matters more than any single print. A multi-week climb confirms a regime change that one volatile session can fake, so the chart above carries more weight than today's number alone.
What Drives an Altcoin Season
Altcoin seasons have followed a recognisable sequence. Bitcoin rallies hard and prints new highs, then pauses to consolidate. Early holders take profits and rotate into large-cap alts, and as those gains compound, capital cascades down the risk curve into mid and small caps. Bitcoin dominance falls as the rest of the market grows faster, and the index climbs as more coins clear the 90-day bar.
The two reference points are 2017 and 2021. During the 2017 to 2018 run, Bitcoin dominance collapsed from roughly 86 percent to below 40 percent as the ICO boom lifted Ethereum, XRP and Litecoin by hundreds of percent, according to CoinGecko. The 2021 cycle repeated the structure in two waves, first DeFi tokens through 2020, then NFTs and memecoins, with dominance sliding from about 70 percent toward 40 percent as Solana and Avalanche ran.
Both cycles shared the same ingredients: a new Bitcoin high, expanding liquidity from loose monetary policy, falling dominance, and retail chasing higher-percentage returns. When those line up, the index follows.
Why 2026 Has Broken the Old Pattern
The 2025 cycle did something the previous two did not. Bitcoin hit a $126,000 record in October 2025, the classic rotation trigger, yet the broad altcoin season never arrived. Its absence has shifted the question from when altcoin season starts to whether the synchronised version still exists.
Several structural shifts sit behind it. Spot ETFs now direct most new demand straight into Bitcoin and, to a lesser extent, Ethereum, and that capital tends to stay put, since institutions rebalance inside a mandate rather than chase rotations. Tradable tokens have meanwhile multiplied into the millions, thinning the capital that once lifted the broader market, while memecoins, perpetual futures and prediction markets soak up the speculative appetite that used to reach mid-cap alts.
What has emerged instead is selective rotation. Capital now moves toward specific assets with institutional-grade signals, active ETF demand, real on-chain revenue, or traditional-finance integration, rather than into altcoins as a class. In May 2026, XRP and Solana products drew fresh capital even as nearly $1 billion left Bitcoin funds in one week, CoinDesk reported, rotation within crypto rather than an exit from it.
Analysts are split. Trading firm Wintermute argues a real revival depends on altcoin ETF mandates broadening, through new products or direct institutional buying, per DL News. Others call it a redefinition rather than a death: the era when a rising tide lifted every token may be giving way to one that rewards a few liquid, revenue-generating networks and leaves the long tail behind.
How to Use the Index in Your Strategy
The index works best as a regime filter rather than a buy or sell trigger. Readings that stay below 25 line up with rising Bitcoin dominance and weak altcoin returns, arguing for a Bitcoin-weighted stance. Sustained moves above 75 usually arrive late in a cycle, after liquidity has broadened, so they help manage risk more than time fresh entries.
Because it only confirms what has already happened, the index pairs best with forward-looking gauges. Read it next to the Crypto Fear and Greed Index for sentiment and funding rates for positioning before you adjust exposure. Tracking your own mix against the regime with a portfolio tracker turns the score into an allocation decision instead of a passive read.
Limitations to Keep in Mind
Equal weighting is the first issue. Because every coin counts the same, a few outsized rallies in small names can lift the score while the broader market stays quiet. The 90-day lookback is the second, smoothing over short rotations and trailing fast regime shifts by weeks, which makes the index a lagging signal.
Coverage is the third, since a top-100 tracker and a top-50 tracker can disagree, putting one platform at 40 and another at 35. The subtler problem is what breadth now means: with rotation concentrated in a few large-caps, a low reading can understate the strength of the names institutions are actually buying.
Final Thoughts
The Altcoin Season Index is still the simplest way to frame Bitcoin against the rest of the market, and tracking it over time cuts through narrative noise better than chasing headlines. The context has changed, though. In an ETF-driven market where rotation has narrowed to a few liquid networks, a low reading says as much about how capital moves through crypto as it does about altcoins.
Use it as one input among several. Pair it with Bitcoin dominance, sentiment and positioning, watch the trend over the daily print, and let it confirm a regime rather than predict one. It will not call tops or bottoms, but it keeps decisions grounded in observable behaviour.
