A blockchain does not have a central server that stores the “correct” version of all operations and decides which transactions are valid. Instead, hundreds or thousands of independent devices continuously exchange data with one another. These devices are called nodes, or blockchain nodes.
Blockchain nodes are what allow Bitcoin, Ethereum, and other decentralized networks to operate without a single central authority. They verify data, distribute information about transactions and blocks, and some of them participate in creating new blocks.
What is a blockchain node?
A node is a device connected to a blockchain network that interacts with other nodes according to the rules of a specific protocol.
Imagine Bitcoin as a huge distributed ledger. There is no single copy stored on a company’s server. Many independent participants around the world maintain copies of the data.
When a new transaction appears on the network, information about it is propagated among blockchain nodes. The nodes check whether the transaction complies with the blockchain’s rules and pass valid data on to other participants.
A similar process takes place when a new block appears: blockchain nodes receive it, verify it independently, and accept it only if it does not violate the protocol rules.
This creates a form of collective verification in which there is no need to trust a single central server.
Why does a blockchain need nodes?
Blockchain nodes perform several key functions:
store blockchain data;
verify transactions and blocks;
transmit information to other network participants;
help maintain a single up-to-date version of the blockchain;
in some cases, participate in creating new blocks.
The exact set of functions depends on the network and the type of blockchain node.
A large number of independent nodes makes a blockchain more resilient. Even if some hardware fails or goes offline, the remaining participants can continue supporting the network.
A distributed architecture also makes it more difficult to manipulate transaction history. Gaining access to a single server is not enough to impose an alternative version of events on the network. This is related to the well-known 51% attack*.
* A 51% attack is a situation in which one participant or group gains control over the majority of a blockchain based on the Proof-of-Work consensus algorithm. This may allow the attacking party to create an alternative blockchain, prevent certain transactions from being confirmed, and attempt to spend its own funds more than once.
What types of blockchain nodes are there?
There is no single classification that applies to every blockchain. The architecture of Bitcoin differs from that of Ethereum, Solana, and other networks, so the types and functions of nodes also vary. Nevertheless, several common types of blockchain nodes can be identified.
Full nodes
A full node independently verifies transactions and blocks according to the protocol rules.
This is an important distinction: a full node does not need to trust a third-party server to determine whether a particular transaction is valid.
For example, a Bitcoin node checks many conditions, including the correctness of the transaction structure, the availability of sufficient funds, the validity of digital signatures, and whether a new block complies with the network rules.
If the data fails verification, the node rejects it.
Full nodes can therefore be viewed as independent blockchain auditors: each of them determines on its own whether network activity complies with the established rules.
Archival and pruned nodes
Full nodes can handle historical data in different ways.
An archival node stores a large amount of blockchain history and allows access to older data.
This is useful for researchers, analytics services, blockchain explorers, and companies that need continuous access to transaction history.
There is also a more storage-efficient option: a pruned node. Such a node initially downloads and verifies the necessary blockchain data and then deletes part of the older information. This significantly reduces disk-space requirements while allowing the node to continue independently verifying the network rules.
Light nodes
Not everyone needs to store hundreds of gigabytes of data. Lightweight nodes are available for devices with limited resources.
Bitcoin uses SPV nodes, or Simplified Payment Verification nodes.
Instead of downloading the full blockchain history, such a node downloads a significantly smaller amount of data and requests the necessary information from full nodes.
This reduces memory, storage, and computing-power requirements. Such solutions are therefore suitable, for example, for mobile cryptocurrency wallets.
The trade-off for this convenience is greater dependence on external nodes: a light node does not have the same level of independent data verification as a full node.
How is a blockchain node different from a miner?
Blockchain nodes and miners are often treated as the same thing, but they are different concepts.
A full node verifies compliance with blockchain rules. A miner participates in creating new blocks.
In Bitcoin and other Proof-of-Work networks, miners perform the computational work required to create new blocks. The transactions included in a block are selected by the miner itself or by a mining pool.
When a suitable block is found, it is propagated across the network. However, the fact that a miner created the block does not mean that other network participants are required to accept it.
Full nodes independently verify the block. If it violates the protocol rules, they reject it.
In other words, miners propose new blocks, while the network of nodes verifies whether those blocks may be added to the blockchain.
To create a block accepted by the network and added to the main chain, a miner receives the reward specified by the protocol, as well as transaction fees from the transactions included in the block. This mechanism is used, for example, in Bitcoin, Litecoin, and Dogecoin.
What is a validator node?
In blockchains that use the Proof-of-Stake (PoS) consensus mechanism, the computational competition between miners is replaced by a mechanism based on staking*.
* Staking is a mechanism for participating in the operation and security of a blockchain that uses Proof-of-Stake (PoS) consensus, in which a participant (validator) locks or commits a certain amount of cryptocurrency as economic collateral. The size and conditions of this collateral depend on the specific network.
A validator locks a certain amount of cryptocurrency and gains the ability to participate in creating or confirming blocks in accordance with the rules of the particular network.
Validators may receive rewards for correct operation. Some protocols impose penalties for serious violations, including the potential loss of part of the locked funds.
However, PoS networks can differ significantly in their design. In some networks, almost any participant who meets the protocol requirements can become a validator. In contrast, in others the number of active participants is limited, and an additional selection mechanism is used.
What are masternodes?
Some cryptocurrency networks use specialized nodes with additional functions called masternodes.
Dash masternodes participate in several network functions, including:
InstantSend — a mechanism for faster transaction confirmation;
CoinJoin — a mechanism for increasing privacy by mixing transactions;
participation in the governance of the Dash ecosystem.
Running such a node requires meeting additional requirements, including providing collateral of 1,000 DASH.
Can you run a blockchain node yourself?
In many public blockchains, yes. This usually requires a computer or server, official or compatible software, a stable internet connection, and sufficient disk space.
However, the requirements vary considerably. One network may run on a relatively ordinary computer, while another may require a powerful server with a fast SSD and a large amount of RAM.
Validator nodes and masternodes may also have financial requirements, such as a mandatory cryptocurrency deposit.
In addition to the initial setup, a blockchain node must be maintained:
install updates;
monitor synchronization;
ensure a stable internet connection;
monitor available disk space;
protect the server against attacks;
keep track of protocol changes.
In other words, running your own blockchain node is not simply a matter of installing an application once and forgetting about it.
Why would an ordinary user need their own blockchain node?
Most cryptocurrency holders do not actually need one. A wallet is usually sufficient for storing, receiving, and sending coins.
However, running your own blockchain node provides something that is particularly valued in the cryptocurrency industry: independence from intermediaries.
Instead of requesting information from someone else’s server, a user can obtain information directly from the blockchain and verify it independently.
This improves privacy and reduces the need to trust third-party infrastructure services.
For developers and businesses, the advantages are even more significant. Exchanges, cryptocurrency exchange services, wallets, and analytics platforms can use their own nodes to:
monitor incoming transactions;
check the number of confirmations;
retrieve blockchain data;
broadcast transactions;
build their own services without constant dependence on external APIs.
There is another reason to run nodes: supporting the network itself.
A blockchain does not exist somewhere “in the cloud.” Infrastructure run by real participants supports its operation. The more independent users operate and maintain their own nodes, the less the network depends on a small number of major server and infrastructure providers.
In this sense, a node is one of the fundamental elements of the blockchain concept: do not trust a single central authority — verify the data yourself.