About the data
This page lists the source and update cadence of every number and what we compute ourselves.
Price data
Our own price database holds over 1.5 million prices at 5-minute resolution since 1 January 2012, plus daily prices from 18 July 2010 (the start of trading on Mt. Gox). We checked the history against several exchanges, and our server keeps storing the current price every 5 minutes. The price itself forms on exchanges; the complete stored history and every calculation built on it are ours.
The US-dollar prices are real historical data. Euro values are converted from the USD price at each day's ECB reference rate, day-accurate across the entire history.
Data sources at a glance
The network data comes primarily from our own Bitcoin node; public services act as failover, provide market and price data, and serve as external reference (inflation, gold). Everything is cached on our side and re-served; every source is named:
Blocks & block height, difficulty, hashrate (7-day average), mempool size, transaction fees and the transactions of the next block, all from our own self-hosted Bitcoin full node with its own mempool instance. The node indexes the whole chain since 2009; the mining history (difficulty and hashrate per day) comes from it too. Primary source for the network data.
Queried live with a freshness check; automatic failover to mempool.space if it is unavailable.
Fallback for network data and live transactions when our own node is unreachable. Used directly only for the balance lookup in "Check address".
Cached as a fallback, refreshed every 30 seconds; balance lookup only on click.
Market capitalisation and trading volume. All-time high and low are computed from our own price database.
Cached, updated every 5 minutes.
Live BTC price in USD and EUR, our primary source for the current price.
Polled every 30 seconds; one value every 5 minutes goes into the price database, with euros converted at the ECB rate.
Daily euro reference rates of the European Central Bank. We use them to convert every stored euro value from the US dollar price, day by day across the whole history.
Published around 4 pm CET, fetched at most every 2 hours; until then the previous day applies.
Counts reachable Bitcoin nodes itself over the Bitcoin protocol (clearnet and Tor). Countries are assigned offline with MaxMind's GeoLite2 database (via geoip-lite), without any external request.
Runs continuously, one cycle after another; the figures are stored per cycle.
Consumer price indices (US, euro area), ECB deposit rate, US Federal Funds rate and the EUR/USD rate: external references for the purchasing power explorer (inflation, savings account, conversion).
Fetched daily and stored on our side; CPI is released monthly.
Gold price (COMEX GC=F) and the iShares Core MSCI World UCITS ETF (Acc, ISIN IE00B4L5Y983, Xetra): external references for the purchasing power explorer.
Fetched on business days and stored on our side.
Computed metrics
Some metrics we compute ourselves from the current block height, with no external licence or third party. These include circulating supply, the share of coins already mined (% mined), the stock-to-flow ratio and energy per BTC. The formulas are publicly known and derive directly from block height.
Not financial advice
Everything on ONLY21 is for information only and is not investment, financial, legal or tax advice. Past performance is no guarantee of future results. Bitcoin is volatile, and you can lose some or all of the capital you commit. Do not make financial decisions based on this site alone. Do your own research and, where appropriate, seek independent, qualified advice.