Data sources and disclaimer
A transparent account of live block APIs, manual cycle coordinates, caching, and failure handling.
Live block height
The primary provider is the Blockstream Esplora API. BtcCal falls back to the mempool.space REST API. Both endpoints returned the same integer block height during verification on 2026-07-17.
Cache and fallback
Successful responses are stored locally with their receive time. A cache under 30 minutes old is labeled “Cached data”; an older one is labeled “Stale data.” If no cache exists, the manual date estimate is used.
Requests occur on entry, tab reactivation, network recovery, and at five-minute intervals.
Manual cycle data
Low/high coordinates live in data/halving-cycles.json. Current values come from the operator reference and remain provisional because no final primary source is attached.
BtcCal does not use confirmed status until both source and selection rule are approved.
Disclaimer
BtcCal is an educational information service. APIs can be delayed or unavailable, and estimated times change with actual block speed. Cycle coordinates and forecast windows are not guaranteed to be accurate and do not constitute investment advice.