Altcoin Season Index
The Altcoin Season Index measures whether capital is currently flowing into alts (index above 75 = Altcoin Season) or into BTC (index below 25 = Bitcoin Season). Computed live on every site build from the top 50 cryptocurrencies' trailing 90-day performance, with stablecoins and Bitcoin excluded from the evaluation set. The gradient bar shows the current reading; the interactive historical chart below shows every month since 2018 with hover tooltips, coloured classification bands, and a Month / Year granularity toggle.
Live index
Percentage of the top 50 coins (excluding stables + BTC) that have outperformed BTC over the trailing 90 days.
Historical context
Altcoin Seasons vs Bitcoin Seasons since 2018. Months since the last Season, average gap, longest streak, and total months for each classification.
Historical Altcoin Season Index
Every month of Altcoin Season Index history since 2018. Lime band (above 75) = Altcoin Season classification; orange band (below 25) = Bitcoin Season classification. Hover any point on the chart for the exact index value, month, and classification.
How often is it actually Altcoin Season?
The strict "Altcoin Season" classification (index >= 75) is historically rare. Across 101 months of post-2018 history:
| Classification | Index range | Months | % of history |
|---|---|---|---|
| Altcoin Season | 75-100 | 4 | 4% |
| Lean alt | 50-74 | ~30 | ~30% |
| Lean BTC | 26-49 | ~36 | ~36% |
| Bitcoin Season | 0-25 | 31 | 31% |
Bitcoin spends roughly 7x more time in Bitcoin Season than in Altcoin Season (31 months vs 4 months). The asymmetry is structural: BTC's gravitational pull on capital reasserts itself faster than altcoins can sustain outperformance. Most "altcoin season" calls in social media refer to the broader "lean alt" zone (50-74) rather than the strict 75+ threshold.
Is it Altcoin Season right now?
No. The current Altcoin Season Index reads 25, which is classified as Bitcoin Season (0-25 band). Only 25 percent of top-50 altcoins have outperformed Bitcoin over the trailing 90 days. The current Bitcoin Season streak began in May 2025 and has now lasted 10 consecutive months, the longest such streak in the historical sample. For an Altcoin Season classification (index >= 75), 75 percent of the top 50 alts would need to beat BTC over 90 days simultaneously.
Longest Altcoin Season vs Bitcoin Season streaks
| Classification | Longest streak | Started | Catalysts |
|---|---|---|---|
| Bitcoin Season (current) | 10 months (ongoing) | May 2025 | BTC ETF inflows + narrow alt outperformance window |
| Altcoin Season (longest) | 2 months | January 2018 | Tail-end of the 2017 ICO mania |
The streak asymmetry is striking: the longest Bitcoin Season run (10 months and counting) is 5x longer than the longest Altcoin Season run (2 months). This is consistent with BTC's role as the crypto market's reserve asset - capital concentration in BTC is the default state, with brief altcoin-outperformance windows opening only during specific cycle phases.
What is the Altcoin Season Index?
The Altcoin Season Index measures BTC-vs-alts rotation as a momentum metric over a defined recent window:
Altseason Index = (top 50 alts beating BTC over 90 days / total alts evaluated) × 100
The convention was popularised by BlockchainCenter around 2020 and has been adopted by Bitbo, Lookintobitcoin, and most major crypto analytics platforms. The index is bounded 0 to 100 by construction.
How to read the index
- Gradient bar at the top of the live index panel: shows the current value with the headline classification ("It IS Altcoin Season!", "It IS Bitcoin Season!", or "It is not Altcoin Season."). The marker line on the bar shows precisely where the index sits within the 0-100 range.
- Interpretation paragraph: plain-English translation of the current value into a cycle-phase read.
- Historical context table (right panel): months since the last Altcoin Season vs the last Bitcoin Season, average gap between season events, longest historical streak, average season length, and total months at each classification. Use this to anchor the current value against historical base rates.
- Interactive historical chart (below): hover any point for the exact index value, month, and classification. Toggle between Month and Year granularity. Fullscreen for analysis.
Classification bands
| Index value | Classification | Reading |
|---|---|---|
| 75 to 100 | Altcoin Season | Three or more out of four top-50 alts have outperformed BTC over 90 days. Historically short-lived (4 to 16 weeks) and tends to occur late in bull markets after BTC makes its cycle top. |
| 50 to 75 | Lean alt | More alts outperforming than not, but below the Altcoin Season threshold. Often the lead-in to a full Altcoin Season classification. |
| 25 to 50 | Lean BTC | BTC outperforming most alts, but not at the extreme. Typical of mid-cycle BTC-led bull phases. |
| 0 to 25 | Bitcoin Season | Only one in four alts (or fewer) outperforming BTC. Capital is concentrated in BTC. Historically coincides with BTC-led legs of bull markets or deep bear markets where alts bleed harder than BTC. |
Methodology
- Live computation. On every site build: fetch the top 50 cryptocurrencies by market capitalisation in AUD with 90-day price-change data from the CoinGecko free public endpoint. Identify BTC's 90-day percentage change. Exclude BTC and known stablecoins from the evaluation set. Count how many of the remaining coins have a 90-day change exceeding BTC's. Divide by total evaluated, multiply by 100, round to nearest integer, bound to 0-100.
- Historical seed. Approximate monthly Altseason Index values from January 2018 onwards (96 months in the seed) provided as context for the current reading. Production builds compute the current value live; the seed handles the historical view.
- Stablecoin exclusion list. Major USD-pegged and AUD-pegged stablecoins are excluded by id (tether, usd-coin, dai, frax, true-usd, binance-usd, paxos-standard, ethena-usde, ripple-usd, paypal-usd, and others). A belt-and-braces filter additionally removes any top-50 coin whose 90-day change is near zero AND whose price is between $0.50 and $2.50 (catches new stables not yet in the explicit list).
- Window choice. 90 days is the BlockchainCenter convention; shorter windows (30 days) produce more volatile values, longer windows (180 days) smooth out short-cycle rotations. The 90-day choice balances responsiveness with noise.
- Resilience. If the upstream source is unreachable during a build, the previous static data file is preserved unchanged.
Limitations
- Window-dependent. Changing the window from 90 days to 30 or 180 days produces different index values for the same date. The 90-day convention is the most-cited but is one of several reasonable choices.
- Top-50-dependent. Coins outside the top 50 can move significantly without affecting the index. A new memecoin pumping 1000 percent is invisible if it isn't yet in the top 50.
- Lagging. The index averages a trailing 90-day window. Rotation that has just started is barely visible; rotation that has run for 90 days appears at full intensity. The index confirms what has happened, not what is about to happen.
- Stablecoin definition is fuzzy. The exclusion list is maintained but new stablecoins enter the market regularly. The belt-and-braces filter catches most of them but edge cases (e.g., volatility-adjusted stables, basket stables) may still slip through.
- Single dimension. The index captures breadth (how many alts beat BTC) but not magnitude (by how much). An Altcoin Season where alts beat BTC by 5 percent is classified the same as one where they beat BTC by 50 percent.
Related tools
- Bitcoin Dominance Chart - stock companion to this index; BTC market cap as % of total crypto, monthly from 2014.
- BTC Dominance vs Altcoin Season Index - how the two indicators relate, with divergence patterns and reading guide.
- Bitcoin Log Regression Bands (AUD) - long-run BTC fair value. Provides absolute price context for the rotation read.
- Bitcoin Rainbow Chart (AUD) - sentiment-labelled version of the log regression.
- Bitcoin Pi Cycle Top Indicator (AUD) - top-zone signal that often precedes a full Altcoin Season classification.
- Crypto CGT Calculator - apply the ATO 50 percent discount to any rotation that triggers a CGT event.
- Crypto Exit Strategy Ladder - build an Altseason-anchored exit ladder for any single crypto position.
Frequently asked questions
The Altcoin Season Index measures the percentage of the top 50 cryptocurrencies (by market capitalisation, excluding stablecoins and BTC) that have outperformed Bitcoin over the trailing 90 days. The convention was popularised by BlockchainCenter around 2020 and has been widely adopted across the crypto analysis community. The index is bounded 0 to 100, with classification bands: above 75 is Altcoin Season (capital flowing into alts), 50 to 75 is Lean alt, 25 to 50 is Lean BTC, below 25 is Bitcoin Season (capital concentrated in BTC). At 75 the historical interpretation is unambiguous: three out of four top alts have beaten BTC over the last 90 days.
On every site build: (1) fetch the top 50 cryptocurrencies by market capitalisation in AUD with 90-day price-change data, (2) identify BTC's 90-day percentage change, (3) exclude BTC and known stablecoins from the evaluation set, (4) count how many of the remaining coins have a 90-day change exceeding BTC's, (5) divide by total evaluated, multiply by 100, round to nearest integer, bound to 0-100.
The 75 threshold comes from the BlockchainCenter convention and reflects a fairly strict definition: three quarters of the top 50 alts beating BTC over 90 days is a high bar. A 50 threshold would trigger an Altcoin Season classification any time slightly more than half of alts outperform, which is too noisy to be useful. The 75 threshold has historically aligned with the most clearly-bullish-for-alts phases of past cycles (late 2017, early 2021). The 25 threshold for Bitcoin Season is the symmetric counterpart: only one quarter of alts outperforming.
Stablecoins (USDT, USDC, DAI, etc) by design have near-zero price volatility against their pegged fiat currency. Including them in the 'outperformed BTC' count would mechanically inflate the index toward 0 in any week BTC is up and toward 100 in any week BTC is down, because stablecoin returns are always near zero. Excluding them isolates the signal to coins that actually carry crypto-market risk. The exclusion uses an explicit list of known stables (USDT, USDC, DAI, FRAX, TUSD, BUSD, USDe, RLUSD, PYUSD, and others) plus a belt-and-braces filter that removes any top-50 coin whose 90-day change is near zero AND whose price is between $0.50 and $2.50.
Not as a standalone rule. The index is a momentum measure of the past 90 days; by the time it crosses 75, the rotation has already happened. Historically the most profitable alt-rotation timing has been when the index was BELOW 25 (alts deeply out of favour, capital concentrated in BTC) - that has marked the floor for alt prices in dollar terms. Using the index as a confirmation signal alongside fundamental views, dominance trend, and your own conviction is more useful than treating it as a trigger. For tax planning around any alt rotation (which is a CGT event in Australia), use the Crypto CGT Calculator.
Historically short-lived. Most Altcoin Season classifications (index >= 75) have lasted 4 to 16 weeks before the index mean-reverts back below the threshold. The longest historical Altcoin Season streak visible in the data set spans roughly a quarter at peak intensity. The asymmetry matters: Bitcoin Season classifications (index <= 25) have historically lasted longer than Altcoin Seasons (average 4.7 months vs 1.3 months in the seed data), reflecting that BTC's gravitational pull on capital reasserts itself faster than alts can sustain outperformance.
Both measure BTC-vs-alts rotation but capture different dimensions. Bitcoin Dominance is a STOCK measure: a snapshot of where capital currently sits, based on total market caps. The Altcoin Season Index is a FLOW measure: how many alts have outperformed BTC over the trailing 90 days, capturing momentum rather than position. The two often move together (rising dominance correlates with falling altseason index) but can diverge. See the dedicated BTC Dominance vs Altcoin Season Index comparison for the full reading guide.
Live computation on every site build from the CoinGecko free public endpoint for the top 50 cryptocurrencies' AUD-priced 90-day price-change data. Historical monthly values (2018 onwards) are seeded from the same methodology applied retroactively, providing context for the current reading. If the upstream source is unreachable during a build, the previous static data file is preserved unchanged.
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