Public, Private, and Permissioned Blockchains

Public blockchains

A public blockchain, like Bitcoin or Ethereum, is open for anyone to join, read, and (subject to the network's rules) submit transactions to, with no central gatekeeper controlling participation. Data is generally visible to anyone who wants to look.

Private and permissioned blockchains

A private or permissioned blockchain restricts who can participate, and sometimes who can even read the data. These are typically run by a single organization or a known consortium of organizations for a specific business purpose, such as internal record-keeping or supply chain tracking among approved partners.

Why the distinction matters

• Trust model: public chains are designed so participants don't need to trust each other individually; permissioned chains rely on trusting the known operating organization(s).
• Transparency: public chain data is generally open; permissioned chain data is typically restricted to approved parties.
• Purpose: public chains suit open, global, trust-minimized use cases; permissioned chains suit controlled, internal, or business-to-business use cases where full openness isn't a goal.

What to remember

• Public blockchains are open to anyone; private/permissioned blockchains restrict participation.
• Most well-known cryptocurrencies run on public blockchains.
• Permissioned blockchains suit controlled, organization-specific use cases.
• The distinction is about trust model and openness, not which one is "more of a real blockchain."