What Is Light Client?
Also known as: Light Node, SPV Client, Lightweight Client, Thin Client
In short
A light client is node software that connects to a blockchain without downloading the whole chain, keeping only limited data such as block headers and verifying the information it needs with cryptographic proofs.
A full node downloads all blocks and transactions and verifies every rule independently; this requires large storage space and continuous bandwidth. A light client, on the other hand, stores only block headers. To verify that a specific transaction was included in a block, it requests a Merkle proof from full nodes and compares this proof against the Merkle root in the block header. This approach on Bitcoin is described as simplified payment verification (SPV) in Satoshi Nakamoto's technical paper.
Light clients let resource-constrained devices such as mobile wallets and browsers access the blockchain without fully trusting a single server. On Ethereum, with the move to Proof of Stake, more efficient light client protocols were developed that rely on the signatures of randomly selected groups of validators, that is, sync committees; this structure is also important for bridges and cross-chain communication.
On the other hand, a light client does not offer security guarantees as strong as a full node. It is more vulnerable to the nodes it connects to withholding some information, and in terms of privacy it can leak to these nodes which addresses it is interested in.
Last updated: · This content is for information purposes only and is not investment advice.