Permissioned vs. Permissionless Blockchain

A permissionless blockchain allows anyone to join the network, run a validating node, and participate in the consensus process without needing approval from any central authority — Bitcoin and Ethereum are both permissionless in this sense, since anyone meeting the technical requirements can become a validator or miner. A permissioned blockchain, by contrast, restricts who can participate in validating transactions to a specific, pre-approved set of entities, typically authorized by whichever organization or consortium controls the network.

This distinction concerns who can validate the network, as opposed to the related but distinct public-versus-private (see Kaavon's "Public vs. Private Blockchain" glossary definition) distinction, which concerns who can read the network's data. A consortium blockchain (see Kaavon's "Consortium Blockchain" glossary definition) is a common real-world example of a permissioned design, where a defined group of organizations jointly controls validation rather than any single entity or an open, permissionless set of participants.