Definition
Simplified Payment Verification (SPV) is the technique, described in Section 8 of Satoshi Nakamoto's Bitcoin whitepaper, that lets a lightweight wallet confirm a payment without downloading the entire blockchain. Instead of validating every transaction, an SPV client keeps only the chain of 80-byte block headers and asks peers for a short proof that a given transaction is included in a block.
How the Merkle proof works
Each block header commits to all of its transactions through a single Merkle root. To prove that a transaction is in a block, a node supplies the transaction plus the handful of intermediate hashes (the Merkle path) needed to recompute that root. The SPV client hashes its way up the path; if the result matches the root in a header that sits under sufficient proof-of-work, the transaction is confirmed as included. This requires only kilobytes of data rather than hundreds of gigabytes.
Trade-offs
SPV trades full verification for efficiency. A light client confirms inclusion and the work behind a chain, but it does not independently check that every transaction obeys consensus rules — it trusts that miners did. Under a 51% attack an SPV client could in principle be shown a valid-looking proof for an invalid chain, so high-value or sovereignty-focused users still favor running a full node.
SPV underpins most mobile and hardware-wallet designs and many second-layer and bridge protocols. For related inclusion mechanics see D-Central's entries on the witness commitment and BitVM.
In Simple Terms
Simplified Payment Verification (SPV) is the technique, described in Section 8 of Satoshi Nakamoto’s Bitcoin whitepaper, that lets a lightweight wallet confirm a payment without…