A real-time spot rate bitcoin price index api published as well. The price displayed in the top menu of Bitcoin.

The BCX is a composite of multiple Bitcoin indices, providing a robust measurement of Bitcoin’s value. Downtime or API changes on any one exchange or constituent index will not drastically alter the quality of the BCX. When the constituent indices publish multiple timeframes, the daily value is chosen for daily BCX construction. The Spot Rate uses the latest data available for each index. The value of the BCX is a quadratic time-weighted average of the most recent data point of each constituent index.