When people hear the word blockchain, Bitcoin is usually the first thing that comes to mind.

That’s understandable. Bitcoin introduced blockchain technology to a huge audience, and it remains one of the best-known examples of a public blockchain.

But blockchain isn’t one fixed design.

A network can be open to everyone, restricted to a single company, shared by several organizations, or designed so that some information stays private while selected information can be verified publicly. There are also scaling systems, such as Layer 2 networks, that operate alongside a blockchain rather than fitting neatly into those four categories.

That difference matters.

A blockchain designed for a cryptocurrency has very different requirements from one used by a group of banks or a company managing internal records. The important questions are fairly simple: Who can join? Who can validate transactions? Who can see the data? And who gets to make the rules?

Those questions lead us to the main types of blockchains.

There is another distinction worth knowing. Blockchain networks can also be described as permissionless or permissioned. That classification focuses more specifically on whether authorization is required to perform certain network functions.

And then there are sidechains and Layer 2 networks. These are primarily scaling approaches, so they shouldn’t simply be added to the four categories as if they describe the same thing.

---

What Is a Blockchain, Exactly?

Forget the technical buzzwords for a moment.

At its simplest, a blockchain is a shared digital ledger. Instead of keeping the record in one place, copies of the ledger can be maintained by multiple computers participating in the network.

Transactions are collected into blocks. Each block is connected to the previous one using cryptographic techniques, creating a history that is difficult to alter without detection.

The network also needs a way to agree on which transactions are valid. That’s where a consensus mechanism comes in.

The basic idea remains similar across many blockchain systems. What changes from one network to another is the way participation is handled.

• Who can read the ledger?
• Who can submit transactions?
• Who can validate them?
• Who controls upgrades?

Who is responsible if something goes wrong? Those differences are what make one blockchain very different from another.

---

1. Public Blockchains

A public blockchain is the model most people associate with cryptocurrency.

The network is generally open, meaning people don’t need permission from a particular company before interacting with it. Depending on the blockchain, participants may be able to run nodes, submit transactions, or help validate the network.

Bitcoin is the classic example. Ethereum is another major public blockchain, although its design and functionality are considerably broader than Bitcoin’s.

The appeal of a public network is straightforward: you don’t have to place the entire system in the hands of one company or institution.

Instead, the rules are enforced by the protocol and the participants following it.

Why Public Blockchains Are Useful

The biggest advantage is openness.

Someone in one country can interact with a public blockchain without first opening an account with the organization operating the network. That property is particularly important for decentralized financial systems and applications designed for global participation.

Public blockchains can also provide a high degree of transparency. On networks where transaction data is publicly available, anyone can independently inspect the ledger rather than relying solely on a company’s internal records.

There’s a trade-off, though.

A system designed to operate without a central authority has to solve the difficult problem of getting many independent participants to agree on the state of the network. That can introduce costs, latency, and other limitations.

Where Public Blockchains Make Sense

Public networks are a natural fit when open participation and reduced dependence on a central authority are more important than complete privacy or centralized control.

Typical examples include cryptocurrency networks, decentralized finance applications, tokenized assets, and smart-contract platforms.

---

2. Private Blockchains

A private blockchain takes almost the opposite approach.

Instead of opening the network to everyone, participation is restricted. A particular organization may decide who can join, who can validate transactions, and what information different participants are allowed to access.

That can make sense in a business environment.

Imagine a company maintaining a shared record between several departments. It may have no reason to let the general public participate in that network. What it actually needs is controlled access and a reliable record that authorized employees or systems can work with.

A private blockchain provides that kind of environment.

The Main Advantage: Control

The organization running a private blockchain can define its rules.

It can determine who gets access, what roles participants have, and how transactions are validated.

Because the participants are known, the network doesn’t necessarily need the same type of open participation mechanism used by a public blockchain. That can make certain private systems faster and easier to manage.

But there’s an obvious compromise.

If one organization controls the network, users ultimately have to trust that organization.

That’s quite different from Bitcoin, where the system isn’t dependent on one company maintaining the ledger.

---

3. Consortium Blockchains

Now imagine a situation where a private blockchain controlled by one company isn’t enough.

Suppose five independent companies need to maintain a shared record. None of them wants to hand complete control to one of the other four.

That’s where the consortium model becomes interesting.

A consortium blockchain is governed by a group of organizations. Rather than one company making all the decisions, participating members share responsibility for the network.

This model is especially relevant when organizations compete in the marketplace but still need to cooperate on certain processes.

Think of supply chains.

A manufacturer, shipping company, customs provider, warehouse operator, and retailer may all need access to information about the same shipment. They have different business interests, but they still need a reliable shared record.

A consortium model can provide that shared environment without requiring one participant to become the sole administrator.

What Makes Consortium Networks Different?

The key difference is governance.

With a private blockchain, one organization typically has primary control.

With a consortium blockchain, authority is distributed among a defined group.

That doesn’t mean every consortium gives every member exactly the same power. The governance rules depend on the implementation. Some participants may have different permissions or responsibilities.

---

4. Hybrid Blockchains

Hybrid blockchains attempt to combine two things that normally pull in different directions: privacy and public verifiability.

The exact design can vary, but the basic idea is easy to understand.

Sensitive operational information remains restricted. At the same time, selected information—or a cryptographic proof that something happened—can be made available for outside verification.

That can be useful when an organization needs to prove something without exposing everything behind the proof.

For example, a company might want to demonstrate that a particular record existed at a certain time without publishing the confidential contents of that record.

The public doesn’t necessarily need to see the entire database. It may only need enough information to verify the relevant claim.

Why Use a Hybrid Model?

Consider a supply-chain company.

Its internal systems may contain contracts, supplier pricing, customer information, and other commercially sensitive material. Publishing all of that data would obviously be a bad idea.

But the company may still want customers or auditors to verify the history of a particular product.

A hybrid design can potentially separate those two requirements.

---

Permissioned vs. Permissionless Blockchains

This distinction causes a surprising amount of confusion.

People sometimes use public and permissionless as if they mean exactly the same thing. Likewise, private and permissioned are often treated as identical.

They’re closely related, but the terms describe different ideas.

A permissionless blockchain generally doesn’t require approval to participate in the relevant network functions.

A permissioned blockchain restricts certain functions to approved participants.

NIST uses this distinction when discussing blockchain systems and notes that permissionless networks allow participants to publish blocks without needing authorization, while permissioned systems restrict that ability.

The distinction becomes useful when looking beyond simple public/private labels.

A network can have separate rules for reading information, submitting transactions, and validating blocks. Those permissions don’t necessarily have to be identical.

---

Sidechains and Layer 2 Networks Are Different

Here’s another area where blockchain terminology gets messy.

Sidechains and Layer 2 networks are often listed alongside the four main blockchain types. Technically, that’s not a very clean comparison.

The first four categories mainly describe access and governance.

Sidechains and Layer 2 systems are primarily concerned with scaling and extending blockchain functionality.

A sidechain is an independent blockchain that operates alongside another chain. It has its own security model and its own validator or consensus arrangements.

A Layer 2 network works differently.

It is built on top of a base blockchain and is designed to process transactions more efficiently while ultimately relying on the underlying chain in a particular way for settlement or security.

Ethereum’s ecosystem includes several Layer 2 approaches, including optimistic and zero-knowledge rollups.

So don’t think of Layer 2 as simply the “fifth type” of blockchain. It’s solving a different problem.

---

Why Do We Need Different Types of Blockchains?

There’s no single blockchain design that maximizes everything at once.

If you want completely open participation, you give up some of the control available in a private environment.

If you want strict confidentiality, you usually can’t also make every record publicly visible.

If you want several competing companies to share control, governance becomes more involved than it would be inside one company.

In other words, blockchain architecture is largely about trade-offs.

Consider a few simple examples.

A cryptocurrency designed for strangers around the world needs a very different trust model from an internal company ledger.

A group of competing shipping companies may need shared governance.

A business dealing with confidential information may want controlled access but still need to prove certain facts to customers or regulators.

And an application struggling with transaction costs may not need a completely new blockchain at all. A Layer 2 solution could be a better fit.

The technology should follow the problem—not the other way around.

---

Where Are Different Blockchain Types Used?

The answer depends heavily on the network’s requirements.

Public

Public blockchains are commonly associated with cryptocurrencies, decentralized finance, digital assets, smart contracts, and open applications.

Their strength is broad participation.

Private

Private networks are more relevant to controlled environments where an organization knows the participants and needs to manage access.

Enterprise record systems are a common example.

Consortium

Consortium networks become attractive when multiple organizations need to coordinate around shared data.

Supply chains and financial networks are examples of areas where this model can make sense.

Hybrid

Hybrid approaches can be useful when confidentiality and external verification are both important.

For example, an organization may want to keep its internal records private while allowing selected facts to be independently verified.

Layer 2

Layer 2 networks are primarily about improving the capacity or economics of a base blockchain.

They can be useful for applications that need more transaction throughput without moving completely away from the underlying network.

---

Which Type of Blockchain Is Best?

There isn’t one correct answer.

That’s probably the most useful thing to understand before choosing a blockchain architecture.

Ask what the system actually needs.

If anyone should be able to participate, a public blockchain may be appropriate.

If one organization needs strict control over access, a private system may make more sense.

If several independent organizations need to share responsibility, consider a consortium design.

If some information must remain private while other information needs to be publicly verifiable, a hybrid approach may be worth exploring.

And if the real problem is transaction capacity on an existing public chain, the answer may be a Layer 2 rather than another base blockchain.

---

---

Final Thoughts

Blockchain technology isn’t a single template that every project has to follow.

Public networks prioritize open participation. Private networks put more emphasis on control and restricted access. Consortium blockchains are built around cooperation between multiple organizations, while hybrid approaches try to balance private information with selective public verification.

Then there are Layer 2 networks and sidechains, which address a different question: How can an existing blockchain handle more activity or provide additional functionality?

That’s why asking “Which blockchain is best?” isn’t particularly useful on its own.

A better question is: What does the system need to accomplish, and who needs to trust whom?

Once those requirements are clear, choosing between public, private, consortium, hybrid, or a scaling architecture becomes much easier.

The label comes second.

The problem comes first.