Stateless clients

Today a full Ethereum node must keep the entire current state, every account balance and contract storage slot, on fast disk, and that state keeps growing. Statelessness flips the model: blocks come with a witness, a proof of exactly the state values they read and write, so a node can verify the block using only the witness and the previous state root.

The goal is to make validating Ethereum possible on modest hardware, even phones, which strengthens decentralisation and lets more people check the chain themselves. In the weak form most likely to arrive first, only block builders store the full state while validators verify with witnesses. It depends on smaller proofs, which is why it is tied to replacing the Merkle Patricia trie with Verkle or binary trees, and pairs with history expiry so nodes need not keep old blocks.

Someone still has to hold the state to build blocks and serve data, which could concentrate that role among specialised operators. Witnesses add bandwidth to every block. Applications that need historical or full state, like explorers and indexers, will still need archive-style infrastructure.