A client is software that communicates with a blockchain network on a user’s behalf. It can be as simple as a wallet app that helps you send and receive crypto, or as complex as a full node program that validates blocks and relays data across the network.
What a client does on a blockchain
At a practical level, a client handles the rules and messaging needed to interact with a blockchain. When you send a transaction from a wallet, the client typically constructs the transaction, asks you to approve it, signs it using your private key (often stored securely on your device or hardware wallet), and broadcasts it to peers or a remote node. Many clients also track balances, display transaction history, estimate network fees, and monitor confirmations by querying the network.
Clients can connect in different ways. Some run locally and talk directly to the peer-to-peer network, while others rely on third-party infrastructure, such as RPC endpoints, to fetch chain data and submit transactions. This design choice affects privacy, reliability, and how much you independently verify.
Types of clients and real-world examples
In crypto, “client” often refers to wallet clients and node clients. A light client verifies only a small portion of blockchain data and depends on full nodes for the rest, which makes it easier to run on phones. A full node client downloads and verifies the chain according to protocol rules, helping secure the network by independently validating blocks and transactions.
On some networks, the term also describes distinct software implementations of the protocol. For example, a blockchain can have multiple compatible clients maintained by different teams, improving resilience by avoiding reliance on a single codebase.