What it connects
Fulcrum sits between a Bitcoin full node and a lightweight wallet. It builds an index that lets the wallet ask for transaction history without downloading the whole chain. The project documentation presents it as an alternative to ElectrumX, using the Electrum server protocol rather than a new wallet interface. The implementation is written in C++.
For Bitcoin, Fulcrum connects to Bitcoin Core or Knots. Its documented requirements include a full node with its transaction index enabled and pruning disabled. That means keeping the chain's old blocks, not just recent ones. Fulcrum adds its own index on top; it does not replace the full node. These are operating requirements, not a claim that a small computer will finish indexing quickly.
What an operator controls
The sample configuration separates the full node connection, index storage and wallet-facing listeners. Operators can configure TCP, encrypted TLS connections and WebSocket endpoints. Running an indexing server is therefore more than opening a wallet: it involves storage, a connection to the full node and deciding which clients may reach the service. This listing is not an installation guide or an independently tested performance result.
Current maintenance and limits
As checked on 20 October 2026, version 2.1.4 was published on 18 October. Its notes describe changes to history lookups and subscription processing, not a new project launch.
The code is distributed under GPLv3. The opened project sources do not establish an incorporated entity or other legal structure, so that field remains Undocumented. No founding year or jurisdiction is inferred from copyright dates, contributor accounts or repository activity.