Bitcoin's share of total crypto market cap · the cleanest cycle-position indicator · pulled from CoinGecko's public API every 60 seconds.
There's a line a lot of seasoned crypto people repeat to newcomers: "Don't watch BTC's price — watch BTC's strength relative to alts." Translated into a number, that's BTC dominance. This tool doesn't draw lines or hand you opinions; it pulls the live data from CoinGecko's public global endpoint, calculates the percentage, and shows you which band you're sitting in right now alongside the historical context. Below: seven sections, including a dedicated US/EU reader section on 2021-05, ETF flows, USDT/USDC stablecoin caps and ETH dominance.
Before getting into the mechanics: a quick mental model. Think of the crypto market as a pool with two faucets and one drain. BTC.D moving up means "the BTC faucet is filling the pool faster than the alt faucet" — capital is flowing into BTC relatively more than into the rest of crypto. BTC.D moving down means the opposite. The total market cap rising or falling is the drain — it tells you whether net capital is entering or leaving crypto as a whole. Reading BTC.D in isolation tells you the relative speed of the two faucets but says nothing about whether the pool is filling or emptying overall. That's why §5 below is the most important section: BTC.D + total market cap + funding rates is the three-indicator minimum for any decision based on this number. Reading BTC.D alone has been the single most common way crypto traders have lost money in the last three cycles, and it's almost always because the price action they thought they were trading (alt season) turns out to be a BTC drawdown alts simply hadn't caught up to yet.
BTC.D = BTC market cap ÷ total crypto market cap × 100%. Put plainly, "across all crypto assets, how big a slice is Bitcoin?" The reason this matters more than spot price for cycle reading is that cycles are about relative strength, not absolute moves. If BTC pumps in a straight line but BTC.D stays flat or rises, that tells you alts are being drained — the rally is structurally "risk-off within crypto," driven by capital fleeing into BTC, not capital flowing into crypto as a whole. If BTC pumps and alts pump harder (BTC.D falling), that's a real risk-on cycle: outside capital is entering crypto, going to BTC first, then dispersing. The chart shows you "BTC went up." Only BTC.D shows you "BTC went up in a way that means alts will also go up." Newcomers fixated on BTC price miss this entirely; they see "BTC hit $110K, must be peak bull" and load alts — except BTC.D has been pinned at 56-58% for months, meaning the rotation never happened, meaning their alt bag goes nowhere.
A useful intuition: imagine BTC.D as the "risk-on switch" inside crypto. When it's high, capital prefers the safest crypto asset (BTC); when it's low, capital is comfortable speculating on far-out alts. The closest traditional-finance analogue is the VIX inverse — when VIX is low, equity flows go from defensive sectors to growth/tech; when VIX is high, capital flees to dividend payers and treasuries. BTC.D operates the same way within crypto. A sudden BTC.D spike from 52% to 58% over four weeks is the crypto equivalent of a VIX spike from 14 to 22 — it's not necessarily catastrophic, but it tells you risk appetite within the asset class has measurably contracted. Trade your positioning accordingly: high BTC.D means defend with BTC, low BTC.D means you have permission to express conviction in alts but the timing window is short.
There's also a structural reason BTC.D is a better cycle indicator than price: BTC's price has a 16-year secular uptrend baked into it, so "price is up" is the default state most of the time and doesn't tell you anything about cycle position. BTC.D has no secular trend — it has oscillated between roughly 32% and 75% across every cycle without breaching either extreme. That bounded oscillation is what makes it useful as a regime indicator; you can't say "BTC at $50K is cheap or expensive" without context, but you can say "BTC.D at 36% is structurally near a cycle top" or "BTC.D at 68% is structurally near a cycle bottom" with reasonable confidence based on 12 years of data points. The asymmetric range is also informative: the high end (70%+) has been touched four times, the low end (35% or below) only twice — implying that "BTC supremacy" is the more frequently visited regime, and "alt supremacy" is the rarer, more euphoric state.
Read this together with the four threshold cards above. BTC.D > 60%: the market only trusts BTC; alts are getting carved up to bedrock-believer holders only. Historically, the best return in this band comes from holding BTC and waiting; alts in this phase are mostly downside. 50-60%: BTC starts the primary advance, large-cap alts (ETH / SOL / BNB) begin to follow, mid-caps are still asleep. This is the band where impatient new participants get killed buying mid-caps "before the rotation" — the rotation hasn't begun yet, the patience hasn't been earned, and most mid-caps just bleed. 40-50%: the genuine alt-season primary advance. Capital fans out to mid-caps, sector leaders start outperforming BTC week-over-week, holding only BTC begins to feel slow. This is when sector-leader baskets typically do well — the L1 leader, the DEX leader, the L2 leader, etc. < 40%: capital has reached meme tokens and micro-caps; rideshare drivers are asking which alt will 10×. Every confirmed instance of BTC.D below 40% (2018-01, 2021-05, 2021-11) has been a phase top. It's not a prediction, it's a pattern.
There are a few additional band-transition signals worth knowing. The most reliable one: the first time BTC.D breaks from a higher band into a lower band, it usually overshoots before stabilising. When BTC.D broke from 60%+ down through 50% in early 2021, it didn't stop at 50% — it ran to 40% in a straight line. When it broke from 50% down through 40% in May 2021, it didn't stop at 40% — it printed 39.99% (basically a kiss of the line) before reversing. Each band crossing is high-volatility for the alts that benefit, which means the optimal entry into an alt-season basket is usually before BTC.D breaks the upper band rather than after, because by the time it has broken cleanly the alts have already done most of their move. The downside is that you can't reliably tell whether the break will happen at all until it does; the upside is that being early to a band-transition trade compounds beautifully if it plays out, because alts do most of their work in the first 30% of the transition.
Counter-trend reading is also valuable. When BTC.D rises sharply from a low (e.g. 40% → 50% within 60 days), that's almost always a sign that an alt-season correction is underway — sometimes mid-cycle (2021-07 correction within the larger bull) and sometimes terminal (2018-02 correction that signalled the start of the bear). The rate of rise matters more than the absolute level: a slow drift from 50% to 55% over four months is healthy BTC leadership; a violent spike from 50% to 55% in three weeks is alts capitulating, which is either a buying opportunity (if total cap is also rising on the same window) or a sell-the-rip signal (if total cap is falling). You need the cross-checks; that's §5.
This tool calls CoinGecko's public global endpoint — free, CORS-enabled, running entirely in your browser; nothing routes through my server. It's normal to see a 0.5-1% discrepancy versus CoinMarketCap or TradingView, because every aggregator computes "total crypto market cap" slightly differently (some exclude stablecoins, others include them; treatment of wrapped tokens and bridged assets varies; survivorship rules differ). The absolute number isn't what matters — direction is. Whether BTC.D moves from 58% to 60% or down to 56% over a given week, all major aggregators agree on direction. The page refreshes automatically every 60 seconds, you can also force-reload with F5. If you ever see "Couldn't reach CoinGecko," check the CoinGecko home page directly — their API occasionally rate-limits or hiccups, and the right move is to wait a minute, not refresh in a loop.
Why CoinGecko specifically rather than CoinMarketCap? Two reasons. First, CoinGecko's API is genuinely free and has a reasonable public rate limit (~10-50 calls per minute on the unauthenticated tier), which means a tool like this can run permanently without me paying for an enterprise plan or proxying through my server. CoinMarketCap's free tier is significantly more limited and harder to embed client-side. Second, CoinGecko's "total market cap" calculation is more transparent — they list which tokens count, which are excluded, how wrapped assets are deduplicated. CoinMarketCap's methodology has changed quietly several times over the years; the historical comparability is weaker. For absolute decimal precision, no aggregator is "right" — the BTC.D number is a model output, not an observed price, so it's always a methodology choice. For directional reading (which is all you should be doing) the choice doesn't matter.
If you want to verify any number on this tool, the procedure is: open coingecko.com → click the "Global" link in the top-right of their homepage → cross-reference the BTC.D percentage and total market cap against what's displayed here. They should match to within rounding error. If they don't, one of two things is happening: (a) the page you're viewing has been cached and a hard refresh will fix it, or (b) CoinGecko has updated their data mid-cycle and the tool just hasn't polled yet — wait 60 seconds and reload. Nothing about this tool requires trust in me as the operator; every datum is verifiable against CoinGecko's own site within two clicks.
Read this with the historical pivots table above. 2017-06, first break below 40%: ERC-20 ICOs raging, every project doing 10× in weeks, BTC felt "boring." By 2018-01 BTC.D bottomed at 32.45% — the all-time low — and everyone said "BTC is finished." Within 60 days the entire alt complex collapsed -95% while BTC.D rebounded to 70%+ over the following year. 2021-05, second break below 40%: DeFi summer's afterglow combined with the Coinbase IPO month. May 19 printed the largest single-day red candle in BTC history and many alts dropped 70% by month-end. 2021-11, the cycle top: BTC.D sat in the 40-41% band, SHIB went vertical, every NFT influencer was minting profile pictures. Twelve months later BTC was -75%, SHIB -90%, Luna at zero. The pattern is unambiguous: lower BTC.D = more alt euphoria = closer to the top. But the inverse isn't symmetric — high BTC.D can either be a bear bottom or an early-bull setup, so you can't read "BTC.D 65%" as automatic "buy alts." You always need a price-trend overlay.
Two more pivots worth committing to memory because they teach the asymmetry of the indicator. 2019-09 BTC.D 70.66%: BTC was around $8,000, alts had been smashed for 18 months, and the market consensus was "BTC is becoming digital gold; alts are dead forever." If you'd interpreted "BTC.D at 70%" as a contrarian "buy alts" signal you would have been right within four months — alts began their multi-quarter accumulation here, and the eventual 2020-2021 cycle paid out 50-100× on top alt baskets. But the signal alone wasn't enough; you needed price action confirmation (BTC bottoming and starting to climb) plus stablecoin cap rising. 2024-09 BTC.D 56.2%: post-ETF approval, capital flowed in but stayed in BTC because of the institutional mandate constraints (most ETF-buyers can't buy alts). This is the example that shows BTC.D's range may have permanently shifted upward in the ETF era — a 56% reading in 2017 would have been mid-band normal, in 2024 it's actually historically elevated for "bull cycle conditions." Don't anchor on pre-ETF historical thresholds blindly; the regime is genuinely different now.
The meta-lesson from these five pivots: BTC.D extremes tell you what is about to break, not what is about to start. At 32% (2018-01) what broke was alt euphoria. At 70% (2019-09) what broke was BTC dominance. At 40% (2021-05) what broke was the first half of the cycle's alt mania. Read extremes as exhaustion signals on the prevailing regime, not as confirmations of the next regime. The transition phase always takes 3-6 months and you need other signals to navigate it (funding rates, on-chain activity, stablecoin caps). BTC.D is the regime exhaustion thermometer, not the regime change clock.
This is where most newcomers blow up. BTC.D falling doesn't automatically mean alts are in a bull — it can also mean BTC fell alone while alts simply didn't fall as much (a "false breakdown"). Two cross-checks are mandatory: (a) Total crypto market cap — is the entire pool growing or shrinking? BTC.D down + total cap up = genuine alt bull (capital is flowing in). BTC.D down + total cap flat = false signal (it's just an internal BTC-share shuffle, no new money). (b) Funding rates on alt perpetuals — the leverage temperature. BTC.D down + alt funding sustainedly positive and elevated = leveraged longs piling on, reversal risk is high. BTC.D down + alt funding neutral or even slightly negative = spot demand is doing the lifting, healthy. Treating any single indicator as a decision input is identical to trading off a single chart pattern — that's how the indicator deceives you. The cross-check isn't optional.
A practical workflow for using BTC.D within a decision frame: each time you want to take a position based on BTC.D, write down the answers to these four questions before you click buy. (1) "What direction is BTC.D moving over the last 30 days, and at what rate of change?" (2) "What direction is total crypto market cap moving over the same window?" (3) "What are funding rates on the top three alts I'm considering — neutral, positive, or extreme?" (4) "What is the BTC price trend (HH/HL or LH/LL on the daily)?" If three or four of these align bullish for alts, you have a real setup; if only one or two align, you're betting on noise. Most retail traders, having taken zero of these steps, simply react to the BTC.D number on its own — which is mechanically equivalent to flipping a coin with extra steps.
There's also a third cross-check worth adding for the ETF era: spot-ETF flow data. Farside Investors and CoinShares publish daily inflow/outflow numbers for IBIT, FBTC, ARKB, ETHA and others. Sustained ETF outflows + BTC.D rising = institutional risk-off in BTC, often presages broader crypto weakness. Sustained ETF inflows + BTC.D flat or falling = institutional money is buying BTC and not crowding alts out (paradoxically alt-supportive because it expands the overall pool). This data is free, weekly, and most retail traders ignore it entirely; it's one of the cleanest information edges available right now.
This section is for US and European readers, where the institutional plumbing has changed dramatically since the January 2024 spot-ETF approval. The simple BTC.D framework I described above was developed during cycles dominated by retail flows; ETF-era cycles modify it in three important ways, and US/EU readers should integrate these before drawing conclusions.
2021-05 in retrospect: peak DeFi summer + Coinbase IPO month. BTC.D printed 39.99% — fractionally below the 40% threshold — and this number is more important now than it was in real time, because we now have eighteen months of hindsight on what 40% means in a maturing market. May 2021 was simultaneously the peak of yield-farming TVL, the Coinbase IPO local-top, the Elon-Tesla-saga whipsaw, and the China mining ban. Every retail and institutional bull case lined up at once. The 39.99% print was the market saying "everyone is in alts as far as the rotation can structurally go." It took 30 months to revisit the 40% threshold from below.
2022-06 BTC.D at 47.5%: the Voyager / Celsius / 3AC unwind. Three months that taught a generation that alt season vanishes faster than it builds. When the Three Arrows liquidation cascade hit, alts dropped 50% in days, BTC dropped 30%, and BTC.D mechanically rose from ~42% to ~47% in six weeks — not because BTC was strong, but because alts were structurally weaker. Rising BTC.D in a downtrend is a different signal from rising BTC.D in an uptrend, and you must read it through the price-trend overlay. Same number, opposite meaning.
2024-09 BTC.D at 56.2%: the institutional concentration era. This is the new world. Spot ETFs (IBIT, FBTC, ARKB, etc.) had pulled in roughly $80B in their first nine months, but >95% of that AUM concentrated in BTC, not ETH (the ETH spot ETF came later and saw much weaker inflows). BlackRock's IBIT alone became the fastest ETF in history to reach $50B AUM. For the first time in BTC's history, dominant capital is structurally biased toward BTC over alts — and that bias is not reversible by simple "alt season rotation", because the inflowing capital (RIAs, family offices, 401(k) allocations) is not allowed to buy alts by mandate. They can buy spot-ETF BTC, sometimes spot-ETF ETH, and that's it. This rewrites the "alt season" thesis: previous cycles assumed that retail BTC profits rotated into alts; ETF-cycle BTC flows mostly come from mandate-restricted vehicles that have no rotation behaviour. The 56.2% BTC.D peak might be the floor for ETF-era cycles, not the ceiling.
USDT and USDC stablecoin market cap: the "dry powder" gauge. Track this alongside BTC.D. When USDT + USDC total market cap is rising sharply but BTC.D is flat, that's capital arriving at exchanges but not deploying — bullish setup if BTC.D then starts falling within 4-6 weeks (capital is moving from sidelines into alts), bearish if BTC.D keeps rising (capital is parking in stables waiting for downside). Stablecoin market cap leads BTC.D moves by about 3-6 weeks historically; rising stables + falling BTC.D simultaneously is the cleanest alt-season setup the market produces. For US readers: USDC is the regulated American option (Circle's New York DFS license, monthly attestations), USDT is the offshore option (Bitfinex / Tether Hong Kong). EU readers under MiCA now have EURC and a few smaller EUR-stables; the data signal is the same regardless of which stablecoin dominates locally.
IBIT inflow timing vs BTC.D. The strongest correlation in 2024-2025 data is between IBIT daily net inflow and BTC.D moves the following week. Heavy IBIT inflows → BTC.D rises (institutional money buys BTC, not alts) → 2-3 weeks later total crypto market cap rises while BTC.D plateaus → eventually some of that money rotates into ETH first, then large-cap L1s. Watch IBIT, not BTC price, if you want to predict BTC.D direction. CoinShares and Farside Investors publish daily IBIT flow data freely; track it.
ETH dominance is tracked separately and you should look at it too. ETH.D = ETH market cap ÷ total crypto market cap. When BTC.D falls and ETH.D rises simultaneously, that's the start of a real alt rotation (ETH is the first beneficiary). When BTC.D falls but ETH.D doesn't rise, alts are pumping but ETH is being skipped — usually that means the rotation has gone past ETH and is firing into L2 / DeFi / meme tokens directly, which is late-cycle behaviour. For L2 (Arbitrum, Optimism, Base) and DeFi-season calls specifically, watch ETH.D — not BTC.D. Tools that show ETH.D alongside BTC.D include CoinGecko's "Global" page and TradingView's CRYPTOCAP:ETH.D ticker.
Three rules for US/EU readers: (1) BTC.D < 40% = late cycle / get cautious on alts. (2) BTC.D > 60% = early cycle / hold BTC, don't chase alts yet. (3) BTC.D 50-60% = mid cycle / mixed positioning. These thresholds were drawn from pre-ETF cycles; in the ETF era the bands may have shifted slightly higher (50-58% might become the new "mid-cycle" band rather than 40-50%), but the directional logic is intact. Reading anything beyond directional logic into these numbers is overfitting.
One last note specifically for US tax-aware readers: BTC.D positioning has tax-loss-harvesting implications most retail investors don't think through. If you sit in an ultra-high BTC.D phase (a bear market low) and decide to swap from BTC to ETH at the bottom — that's a taxable event in the US (LTCG if held >1 year, STCG if shorter). The 30-day wash sale rule does not currently apply to crypto in the US (the IRS has signalled intent to extend it but has not, as of writing), but state rules vary and the federal landscape changes. For European readers under MiCA, swap events are also generally taxable, with country-specific rules on capital gains (Germany 0% after 1 year hold, France ~30% flat rate, UK CGT thresholds, etc.). If you're using BTC.D to rotate between BTC and alts dynamically, factor in the after-tax return — sometimes a clean 70/30 BTC/ETH hold beats active rotation simply because every swap is friction. The numbers in this tool are pre-tax; the decisions you make from them aren't.
→ How to call bull vs. bear · my dumb-but-honest method (BTC.D is one of five signals; this article puts them together)
→ Bitcoin halving · 4-cycle recap (the relationship between halving cadence and BTC.D rotation cadence)
→ BTC full-history chart + halving countdown (the long-horizon price companion to this tool)