What is a node in crypto?

A node is a computer that runs a blockchain’s software, keeps a copy of the blockchain ledger and checks every new transaction and block against the network’s rules. Thousands of nodes around the world connect to each other, share blockchain data and together make sure nobody can change the record on their own.

What is a blockchain node?

A blockchain node is any device that connects to a blockchain network and takes part in it. Most nodes do three things: they store blockchain data, they verify transactions and blocks, and they pass valid information on to other nodes. There is no head office; the network is simply the sum of its nodes.

A node is not the same as a crypto wallet or an exchange. A wallet holds the keys that control your coins and needs a node to see the blockchain. If you use an exchange or a typical mobile wallet, you rely on nodes run by the company. Running your own node means you check the data yourself.

What a node does depends on the blockchain technology behind it. On Bitcoin, nodes check proof of work; on Ethereum, nodes follow the validators who propose blocks under proof of stake.

How blockchain nodes work in a blockchain network

Blockchain nodes work like a group of independent bookkeepers who all keep the same ledger and check each other’s work:

1. A transaction arrives. When you send crypto, your wallet broadcasts the transaction to one or more nodes.
2. Nodes check it. Each node verifies the signature, checks that the coins exist and haven’t been spent, and confirms the fee and format follow the rules.
3. Nodes pass it on. Valid new transactions spread across the network in seconds. Invalid ones are dropped.
4. A block is added. A miner or validator bundles transactions into the next block. Nodes check the block, add it to their local copy and stay synchronized with the rest of the network.

Because every full node checks everything for itself, a fake transaction or a block that breaks the rules is rejected, no matter who sends it.

Types of blockchain nodes

There are several node types, and they differ mainly in how much data they store and what they verify.

Full nodes

Full nodes download and verify the entire blockchain history, from the first block to the latest, and enforce every rule. They are the backbone of network security. A pruned full node verifies everything too, but deletes old block data after checking it to save storage. Bitcoin Core can prune down to well under a gigabyte.

Light nodes

Light nodes, or lightweight nodes, store only block headers and ask full nodes for the details they need. Bitcoin’s version is called simplified payment verification (SPV). Most mobile wallets use light nodes: fast and convenient, but you trust the full nodes they connect to.

Archive nodes

Archive nodes keep full historical data, including every past state of the blockchain, not just its transaction history. Block explorers, analytics firms and developers use them. On Ethereum, an archive node needs many times the storage of a regular full node.

Miner nodes and validator nodes

Miner nodes are full nodes that also compete to create new blocks with proof of work, as explained in our page on mining. Validator nodes do the same job on proof of stake chains: on Ethereum, a validator needs a stake of 32 ETH. Most nodes are neither; they only check and relay.

How nodes keep the blockchain secure

Nodes keep a blockchain secure by making cheating pointless. Every full node holds a complete copy of the blockchain and checks new blocks independently, so there is no single server to hack or switch off. If a miner or validator tried to create coins out of thin air, honest nodes would reject the block.

This is what decentralization means in practice: the more independent node operators there are, in more countries, the harder it is for any company or government to censor transactions or rewrite the rules.

Running a node: hardware requirements and costs

Running a node has become cheap enough for hobbyists, but the hardware requirements differ per network:

• Bitcoin full node. A personal computer or a small device such as a Raspberry Pi, a fast SSD with room for several hundred gigabytes of blockchain data (or a pruned setup), and a reliable internet connection without a tight data cap.
• Ethereum full node. Two pieces of software (an execution client and a consensus client), a fast SSD of around 2 TB and more memory. Many people use dedicated hardware.

A Raspberry Pi node: a worked example in euros

Say a Raspberry Pi node uses 10 watts and runs all year, and your electricity costs €0.30 per kWh (check your own contract):

• Energy per year: 10 W × 24 hours × 365 days = 87.6 kWh
• Cost per year: 87.6 × €0.30 = €26.28

The hardware is a one-off cost on top of that. The first sync, when your new node downloads and checks the whole blockchain, can take from several hours to a few days.

How to set up your own node

If you want to try, the setup follows the same steps on most networks:

Developers who need reliable access without running hardware often use a cloud provider or node-hosting service instead. That is convenient, but you are back to trusting a third party.

Nodes and EU rules

Running a node for your own use is not a crypto-asset service under MiCA, so you don’t need a licence. Licensed exchanges and custodians run their own nodes to process transactions for their customers. When you withdraw to your own wallet, the EU travel rule may require the exchange to check that the self-hosted wallet is yours for transfers above €1,000. Running your own node doesn’t change that check, but it does mean your wallet no longer reports your addresses to someone else’s server.

Should you run a crypto node?

Running a node makes sense if you hold bitcoin in self-custody and want to verify your own transactions instead of trusting someone else’s data. It also supports the network. It does not earn you money, and it won’t protect you from losing coins if you lose your keys.

If you only buy small amounts on an exchange, you don’t need one. In the EU, licensed exchanges run their own infrastructure, and our guide to wallet types explains when moving coins to your own wallet is worth it. Whatever you do, remember that crypto is volatile and you can lose all the money you invest.

Related terms

• Blockchain
• Validator
• Consensus mechanism
• Decentralization
• Mining