How Do ‘Simplified Payment Verification’ (SPV) Wallets Use Merkle Trees?
SPV wallets are lightweight wallets that do not download the entire blockchain. Instead, they only download the block headers.
To verify that a transaction is legitimate and included in a block, the SPV wallet requests a Merkle Proof from a full node. The Merkle Proof, along with the Merkle Root in the block header, allows the SPV wallet to cryptographically confirm the transaction's inclusion without needing the full transaction data.