A permissionless blockchain is open to anyone. No approval is needed to join, validate transactions, or even build applications on it. Bitcoin and Ethereum are the most famous examples.
Accessibility: Anyone with an internet connection can participate.
Decentralization: No central authority controls the network.
Transparency: All transactions are visible on the public ledger.
Security: Relies on cryptographic consensus mechanisms (like Proof of Work or Proof of Stake, PoS vs PoW) to prevent fraud.
Best use cases: