Differences between lightweight and full nodes

In general, lightweight nodes and full nodes serve different purposes in blockchain networks, with very different resource requirements and functionalities.

Full nodes store a copy of the whole blockchain and maintain a copy of the ledger. They participate in the validation of transactions and the verification of blocks. They download and store every block and every transaction. This is where independent verification of the history of the blockchain is done to ensure its accuracy and security. Full nodes contribute to decentralization and network security through the enforcement of consensus rules. They require enormous storage, bandwidth, and computational resources to store and process the large data size of a blockchain. Running a full node entails users with the utmost control and trust over the data since they depend solely on their verification processes and not from other nodes.

On the contrary, lightweight nodes (SPV-Simplified Payment Verification) nodes do not store the whole blockchain. Instead, they download just block headers, which contain the compact summaries of the blocks in place of all transaction data. Therefore, they can validate the correctness of a transaction by querying full nodes, without themselves validating every transaction. Lightweight nodes are ideal for resource-constrained devices, such as smartphones, because they require significantly less storage and bandwidth. However, they rely on full nodes to pull transaction details. Because of this, they are less secure and more reliant on network participants in terms of data accuracy.

While full nodes make up for decentralization and security, lightweight nodes make up for accessibility and efficiency; that is the reason they could be practical for regular users ready to interact with the blockchain without resource claims to keep a full node.

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~ Nesaty