Electrum
Electrum is a lightweight, open-source Bitcoin wallet software that prioritizes security and speed. It operates as a thin client, meaning it does not require downloading the entire Bitcoin blockchain, instead connecting to external servers for transaction data. It is known for its support of hardware wallets, multi-signature setups, and advanced features like coin control and fee estimation.
Developers should learn Electrum when building or integrating Bitcoin-based applications that require a secure, efficient wallet solution without the overhead of a full node. It is particularly useful for scenarios involving hardware wallet integration, multi-signature transactions for enhanced security, or applications needing fast synchronization and low resource usage, such as mobile or embedded systems.