What is a blockchain node? Full nodes, light wallets and running your own

Every blockchain depends on computers that keep a copy of it and check that new transactions follow the rules. Those computers are called nodes. You don’t need to run one to use crypto, but knowing what they do explains a lot about how bitcoin and Ethereum stay honest, and why your wallet is trusting someone when it shows you a balance.

This guide covers what nodes do, the different types, what running your own involves, and how it differs from mining and staking. If you’re new to the basics, start with what is a blockchain?

What a node is

ethereum.org describes a node as any instance of the client software connected to other computers also running the software. Bitcoin.org describes a full node as a program that fully validates transactions and blocks.

Nodes do three jobs:

• Check: every transaction and block is tested against the network’s rules before it’s accepted.
• Pass on: valid transactions and blocks are relayed to other nodes, which check them again.
• Serve: nodes provide data to lightweight wallets that don’t keep the whole blockchain.

Because many independent nodes check the same data, no single company decides what the blockchain says. ethereum.org lists enforcing the consensus rules and supporting decentralization among the things nodes do for the network.

Full nodes and light wallets on Bitcoin

A full node downloads the whole blockchain and checks it from the start. Bitcoin.org explains that full nodes also help the network by accepting transactions and blocks from other nodes, validating them and relaying them. Without enough of them, it says, lightweight clients couldn’t connect through the peer-to-peer network and would have to rely on centralized services instead.

Most phone and desktop wallets are lightweight. The original bitcoin white paper describes how this works, under the name simplified payment verification: a wallet keeps only the block headers and checks that a transaction is included in a block. That’s reliable while honest nodes control the network, but more vulnerable if an attacker overpowers it. See the bitcoin white paper explained and what is a 51% attack?

The trade-off is trust. A light wallet relies on the nodes it connects to for its view of the blockchain. A full node checks everything itself.

Nodes on Ethereum

Since The Merge, when Ethereum moved to proof of stake, a node runs two pieces of software working together:

• an execution client, which handles transactions and the state of accounts and smart contracts;
• a consensus client, which follows the proof-of-stake rules that decide which blocks are part of the chain.

ethereum.org describes three types of node:

What running your own node takes

Bitcoin. Bitcoin.org’s guide is written for Bitcoin Core, the main full node software. It lists:

• disk space: the full blockchain takes over 750 GB, though pruned mode cuts that to around 7 GB (the smallest setting is 550 MiB of block data);
• at least 2 GB of RAM;
• a broadband connection with upload speeds of at least 400 kilobits per second;
• data use that can reach 200 GB uploaded a month, 20 GB downloaded a month, plus around 740 GB the first time it syncs;
• running at least 6 hours a day, though running continuously is better.

Ethereum. ethereum.org lists a minimum of 4 to 8 GB of RAM and a 2 TB SSD, noting that an SSD is necessary for the write speeds required, and recommends a wired internet connection. It says plainly that you don’t need any ETH to run a node.

Both blockchains grow every day, so treat these figures as a snapshot and check the current guidance before buying hardware.

Node, miner or validator?

Running a node is often confused with earning crypto. They’re different roles:

• A node checks and passes on transactions and blocks.
• A miner on Bitcoin competes to create new blocks using computing power. See bitcoin mining explained.
• A validator on Ethereum helps create and confirm new blocks with ETH at stake, and running your own validator requires 32 ETH, according to ethereum.org. See what is crypto staking?

Validators need a node to do their job, but running a node on its own doesn’t make you a miner or a validator.

Why people run their own

ethereum.org sums up the main reasons:

• Verify for yourself. Every transaction is checked locally, so you don’t have to trust anyone else’s version of the blockchain: “don’t trust, verify”.
• Privacy. Your wallet can use your own node instead of someone else’s, which ethereum.org lists as a privacy benefit.
• Supporting the network. More independent nodes means more copies of the data and more places enforcing the rules.

The downsides

Bitcoin.org is frank about the costs and risks:

• Bandwidth. Some internet providers may cut off a connection that uses a lot of data, without warning.
• Legal limits. Bitcoin use is prohibited or restricted in some places.
• Security. Antivirus software may quarantine blockchain files, and a node can become an attack target.
• Upkeep. You’ll need to install updates and keep the machine running.

Three common mix-ups

• “My coins are stored in my node.” A node keeps a copy of the blockchain, which records who controls what. Control comes from the private keys in your wallet, whether or not you run a node. See public and private keys explained.
• “I need a node to send a transaction.” You don’t: light wallets send transactions through nodes run by others.
• “Running a node means mining.” It doesn’t, as the section above explains. Mining and validating are separate roles that need a node, not the other way around.

Should you run one?

If you use a wallet on your phone and hold modest amounts, a light wallet is normal and perfectly usable. Running a node makes more sense if you value privacy, want to check your own transactions without relying on anyone, or hold larger amounts in self-custody. Either way, a node doesn’t protect your keys: that depends on how you store your seed phrase.