Altcoin Season Index

The Altcoin Season Index plots a single 0–100 composite against the right axis — the share of the top-50 cryptoassets, with stablecoins and asset-backed tokens excluded, that have outperformed Bitcoin over the trailing 90 calendar days. Four tinted zones split the plot. Bitcoin Season sits at or below 25 in deep slate; the BTC-leaning band runs 25 to 49; altcoin-leaning runs 50 to 74; the rust-toned Altcoin Season zone sits at or above 75. Bitcoin’s USD price runs muted on the left log scale for cycle context.

Today’s reading is 36 — BTC-leaning. The 7-day rolling mean is 38; the 30-day mean is 37. The series spans 3,298 daily observations from April 2017 to the most recent close. Index values refresh overnight; spot in the reading row above auto-refreshes a few times a day in the browser.

The methodology is short enough to quote intact. The canonical statement reads:

If 75% of the Top 50 coins performed better than Bitcoin over the last season (90 days) it is Altcoin Season.

With a single exclusion clause: Excluded from the Top 50 are Stablecoins (Tether, DAI…) and asset backed tokens (WBTC, stETH, cLINK,…). Cryptoasset markets clear continuously, so “90 days” is 90 calendar days, not 90 trading days. The Top 50 is rebalanced daily as market-cap ranks shift.

At any date t, the index is the share of the eligible sample whose return over the prior 90 days has beaten Bitcoin’s, multiplied by 100. The value rounds to the nearest integer when the sample size is exactly 50; in practice the eligible cohort drifts a few names around 50 as wrapped assets and new stablecoin issues enter and exit the top-cap list.

Two reconstruction notes. Provenance for the sample list and the 90-day return calculation is documented on the data sources page; the daily index print on this chart matches the canonical methodology within rounding. Different publishers run the same methodology against different baskets: one site uses the top 50, another the top 100. That divergence has its own section below. For the formula and window choices we ship, see the methodology page.

The index reads rotation, not price. Sustained readings above 75 mark full altcoin seasons — risk-on capital spilling out of Bitcoin and down the cap stack. Sustained readings below 25 mark BTC-led regimes — capital consolidating into the most liquid asset, historically during late-bear capitulations and the opening leg of the next bull. Crossings of the 50 line mark the handover, but the meaningful regime shifts happen at the 25 and 75 thresholds, not the midpoint.

Reading the index against canonical cycle anchors surfaces the rotation pattern with no commentary needed. The 2017 cycle top printed deep in Altcoin Season (ICO mania — everything was outrunning Bitcoin); the 2018 cycle low pulled back into the BTC-leaning band as alts collapsed faster than BTC. The May 2021 altseason peak printed at the very top of the scale; the November 2021 cycle top was a quieter altcoin regime by comparison; the 2022 post-FTX low capitulated into Bitcoin Season. The full anchor list:

A different cut of the same data: how many days each cycle has spent in each zone. The index series begins April 2017, so the 2012 and 2016 halving cycles predate coverage. We anchor cycles on the 2020 and 2024 halving block-confirmation dates — block 630,000 on 2020-05-11 and block 840,000 on 2024-04-19. The pattern is asymmetric and worth pausing on: the BTC-leaning band hosts more days than any other zone in every cycle, and full Altcoin Season — the 75+ band — is rare in absolute terms.

One of the things this chart does not advertise is that “the Altcoin Season Index” refers to a methodology, not a single canonical reading. The 75-of-50 construction was popularised by blockchaincenter.net, and a top-100 variant runs on CoinMarketCap’s panel. The two implementations agree on the threshold (75%) and the window (90 days) but disagree on the basket.

The disagreement matters most in transitions. When the 51st–100th-cap cohort outperforms the top-50 — the usual mid-cap-front-running pattern early in a rotation — the top-100 index turns altcoin-season first. When the 51st–100th-cap cohort underperforms (early-bear trash-take selloffs), the top-100 index decays first. Same threshold, same window, different reading on the same day. We ship the top-50 form because the methodology page’s verbatim definition specifies “Top 50” in plain text; readers cross-checking against the top-100 panel will see a different number with a parallel meaning.

The Top-50 universe also drifts cycle-over-cycle. In 2021 the sample leaned heavily DeFi (UNI, AAVE, COMP) and meme-tokens (DOGE, SHIB); in 2024 the sample leaned L1-infrastructure and restaking (SOL, AVAX, ETH-restakers). Comparisons across cycles are sample-robust but not cohort-identical — what counts as a top-50 altcoin in 2026 is not what counted in 2021.

For a dollar-cost-averaging investor. Functionally none. The index is a cohort rotation gauge measured against Bitcoin; a steady weekly buy operates below its timescale. Skim the regime line for cycle texture; otherwise this chart is not for you.

For a cycle-timing trader. Treat the 75 crossing as a confirmation that an alt rotation has been underway for weeks, not a trigger that one is about to begin. The 90-day window means the index is a lagging indicator by design; the OTHERS market-cap line and the Bitcoin Dominance reading move earlier. The 25 crossing in the other direction is the cleaner contrarian setup — sustained readings below 25 have bracketed every cycle-bottom window on the index’s record. Pair with the stablecoin float for the dry-powder view.

For a researcher. The series, the rolling means, and the daily timestamps are the only inputs the chart needs. The methodology page lists every choice — Top-50 sample, 90-day window, daily rebalance, stablecoin and wrapped-asset exclusions — and flags the canonical-vs-alternative basket sizing question explicitly.

The 90-day window lags meaningful regime shifts by 30–60 days. The index is a backward-looking 90-day rolling counter; rotations show up in smaller-cap market-cap aggregates and in the dominance line weeks before the trailing-90-day return calculation can register. Most of the trader-side critique of the index — that it confirms what was already obvious — rests on this construction. Treat 75 crossings as confirmation; the leading edge of rotation lives elsewhere.

Top-50 versus top-100 basket sizing produces different readings. The canonical 75-of-50 form and the top-100 variant can disagree by 10–20 points during transitions. We ship the top-50 form because the methodology page’s verbatim definition specifies it; the top-100 panel will print a different number on the same day with a parallel meaning. Read either; do not splice the two.

Sample composition changes cycle-to-cycle. The top-50 universe in 2021 leaned DeFi and meme-tokens; in 2024 it leaned L1 infrastructure and restaking. Comparing the 2021 alt-season peak to the 2024 alt-season peak compares two different sets of alts — the same 75-threshold reading, but a different cohort. Cycle-over-cycle comparisons are robust to the fact that the basket has shifted; they are not robust to the question of what specifically rallied.

Stablecoin issuance does not move this chart. Bitcoin Dominance reacts mechanically to stablecoin mints and burns — the stablecoin slug sits in dominance’s denominator. The Altcoin Season Index excludes stablecoins entirely, so a $5B USDT issuance on a quiet Sunday rotates dominance without touching this index. The two charts agree most when the rotation is altcoin-driven; they disagree most when the move is stablecoin-driven. When they disagree, the disagreement is the signal.

Canonical questions from Google’s “People also ask” block for altcoin season, answered against the data on this page.