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Blocks & network · 2 min read

What is a peer-to-peer network?

By Oliver James Whitmore · Updated 20 October 2026

In one sentence

A peer-to-peer network is a network in which computers connect directly to each other as equals, sharing data without routing it through a central server.

Gossip: a new transaction (amber) reaches its peers (indigo), which pass it to theirs (teal).Each node checks what it hears before passing it on
Gossip: a new transaction (amber) reaches its peers (indigo), which pass it to theirs (teal).

How it works

In a client–server system, everyone talks to the same server, and if the server goes down, so does the service. In a peer-to-peer (P2P) network, each participant is both client and server. A blockchain node keeps connections to a small number of peers and accepts connections from others.

Information spreads by gossip. When a node hears about a new transaction or block, it checks it and then tells its peers, who check it and tell theirs. Because each step multiplies the number of nodes that know, a new block usually reaches most of the network within seconds, even though no node is connected to more than a tiny fraction of the others.

New nodes need a way in. Bitcoin software starts from a list of seed addresses and then learns more addresses from peers. Ethereum nodes use a discovery protocol based on a distributed hash table, an idea that goes back to the Kademlia design published in 2002.

The design has no single switch to turn off, but it has its own weak points. A node that is surrounded only by an attacker's peers — an "eclipse" — sees whatever the attacker chooses to show it. Client software therefore tries to keep connections diverse.

A simple example

Picture news in a village with no newspaper. You tell three neighbours; each of them tells three more who had not heard; after a few rounds almost everyone knows, and the person who started it never had to visit every house. Gossip in a blockchain network works the same way, except that every listener checks the story before repeating it.

Common misconception

Misconception: Peer-to-peer means private: nobody can see what I do.

In fact: Peer-to-peer describes the shape of the network, not privacy. Transactions are broadcast to everyone, and the peers you connect to can see your IP address unless you take extra steps.

Where you meet it

  • Bitcoin, Ethereum and almost every public blockchain.
  • File sharing systems such as BitTorrent.
  • Explanations of why a blockchain is hard to shut down by targeting one company.

Sources

This card explains a technical concept for general education. It is not a recommendation to acquire, sell or hold any crypto-asset, and it is not financial advice.