Crypto glossary
Verkle tree
A Verkle tree is a data structure proposed for Ethereum's state that uses vector commitments to make proofs far smaller, a step toward stateless clients.
The name blends vector commitment and Merkle tree. Like a Merkle tree, it commits to a large set of data with a single root, but instead of hashing child nodes together, each node uses a vector commitment that can prove any child's value with a small, constant-size proof. Nodes can therefore be very wide, keeping the tree shallow and proofs short.
For Ethereum, that would shrink the witness needed to prove all the state a block touches from potentially megabytes to a few hundred kilobytes or less. Small witnesses would let validators verify blocks without storing the full state, which is the goal of statelessness and part of the roadmap stage known as the Verge. Verkle trees were specified in detail and tested on dedicated test networks.
Plans have shifted. Verkle commitments rely on elliptic curve assumptions that a quantum computer could break, and advances in proving hash-based structures with zero-knowledge proofs led researchers to consider binary Merkle trees instead. Any state tree migration would also be one of the most complex upgrades in Ethereum's history, so timelines remain uncertain.
Example
Under a Verkle design, a validator receiving a block also receives a compact witness proving every account it touches, and can verify the block without keeping hundreds of gigabytes of state on disk.