Public, private and permissioned blockchains
Who can join, who can validate and who can read the data: the main types of blockchains and their trade-offs.
"Blockchain" describes a family of systems. They differ in who can participate and who can see the data.
Public, permissionless blockchains
Anyone can run a node, send transactions, read the full history and — depending on the consensus — take part in validation. Bitcoin and Ethereum are examples.
- Strengths: open access, censorship resistance, independent verification.
- Trade-offs: limited throughput, public transaction history, fees that rise with demand.
Private blockchains
One organisation controls who can join and validate. Data can be hidden from outsiders.
- Strengths: speed, privacy, control.
- Trade-offs: participants must trust the operator; it is closer to a shared database than to an open network.
Consortium (permissioned) blockchains
A group of organisations runs the network together. Only approved members validate, while access to read data can be open or restricted. Such networks are used for supply chains, inter-bank settlement and record keeping between companies.
Public networks with permissioned layers
Some designs mix both worlds: an application on a public chain can restrict who uses it, or a private network can periodically publish proofs to a public chain.
Why the distinction matters
- Trust: on a public chain you verify the rules yourself; on a private one you rely on the operator.
- Transparency: public ledgers show every transaction; addresses are pseudonymous, not anonymous.
- Tokens: most tradable cryptocurrencies live on public blockchains.
Learn the basics in What is a blockchain?.
Blog posts are for education and information only and are not investment, legal or tax advice.