What Are Nodes in a Blockchain?

Nodes are the backbone of a blockchain — they are the computers that make up a blockchain network. They:

• Are distributed across the world;
• Contain the blockchain database and the software that runs the blockchain;
• Run software to help maintain the blockchain network;
• Provide the computing resources needed to perform the functions of the blockchain;
• Store and verify transactions (which then form a permanent record on the blockchain).

Some nodes may specialize in certain functions, such as maintaining a list of networked peers or managing the network's consensus protocol.

There are thousands of nodes in a single blockchain network, distributed across the world and independent of each other. Each node runs its own copy of the blockchain software, which stores data about all previous transactions on their blockchains (the chains).

Nodes aren't directly controlled by anyone; instead, they act as independent agents who receive incentives (such as earning cryptocurrency rewards) for participating in these networks and verifying transactions on them. The goal is to maintain a shared ledger, where:

• All transactions are recorded on the blockchain, and each node has a copy of that ledger;
• It's possible for anyone who has access to the blockchain's ledger to verify that any transaction took place as recorded;
• Each node verifies transactions to ensure they are valid.

The nodes are therefore like bookkeepers: they keep track of who owns what and when it was created/destroyed, while verifying that all actions taken by others were legitimate (i.e. not fraudulent).