> ## Content Index > Fetch the complete content index at: https://www.cryptowithblock.com/llms.txt > Use this file to discover other available public pages before exploring further. # Nodes: Who Keeps the Copies - URL: https://www.cryptowithblock.com/nodes-who-keeps-the-copies/ - Published: 2026-10-31T11:02:17.000Z - Updated: 2026-11-06T15:03:02.000Z - Description: Nodes are the thousands of computers that keep and check the blockchain ledger. Learn what they do, who runs them, and what your wallet trusts every time you open it. - Author: Crypto With Block - Tags: How Blockchain Works, #lesson ## Who keeps the copies Hi, I'm Block. There's no headquarters for Bitcoin. No main server you could walk up to and unplug. So where does the ledger actually live? In this lesson: what a node is, what it checks, who runs them, and what your own wallet is quietly trusting every time you open it. ## What is a node? In the last lesson, we saw each block chained to the one before it, and I said thousands of computers check those links. Those computers are called nodes. A node is simply a computer running the network's software, connected to other computers running the same software. Picture a huge library where volunteers all over the world each keep a complete copy of the same record book, and compare notes with each other all day long. There's no master copy hidden in a vault. Every full copy is just as real as the others. > Every full copy is equally real. How many are there? Nobody can count them exactly, because anyone can run one, and many don't advertise themselves. Trackers see thousands of them, run by people and companies all over the world. The copies are spread across the world, not kept in one place. > No single place holds the copy. ## A node's three jobs So what does a node actually do all day? Three jobs. It receives new transactions and blocks from its neighbors. It checks every one of them against the rules. And it passes the good ones along, while the bad ones go nowhere. Receive, check, pass it on. > Receive, check, pass it on. Here's what passing along looks like. Your wallet hands a transaction to one node. That node checks it and hands it to its neighbors, who check it and hand it to theirs. It spreads node to node, like news through a crowd, until the whole network has it. No central switchboard. Just neighbors passing it on. > No switchboard. Just neighbors passing it on. The checking is the heart of it. For every transaction, a full node asks: is the signature valid? Do these coins exist? Have they already been spent? For every block: does it link to the right parent, and does it follow every rule? If anything fails, the node throws it away. > Fail one check, and it's thrown away. Here's the part people miss. A full node doesn't take anyone's word for anything. Not the computer that made the block, not the node it heard it from, not the biggest company on the network. It checks everything for itself, all the way back to the very first block. > A node checks everything itself. Here's a real test of that. In August twenty ten, someone exploited a bug in Bitcoin's software and created more than one hundred eighty-four billion bitcoins in a single transaction. That's thousands of times more than should ever exist. > Far more than the 21 million limit. Within about five hours, a fixed version of the software was out. As node operators upgraded, their nodes rejected the bad transaction for breaking the rules. By the next day, the corrected chain had overtaken the bad one, and those billions of coins simply stopped existing. > Break the rules, and the coins don't count. ## Nodes enforce the rules That's the real power nodes hold. Some computers produce new blocks, but every node decides for itself whether a block is valid. A block that breaks the rules is worthless, no matter who made it or how much work went into it. The rules are enforced by everyone who runs a node. > Everyone running a node enforces the rules. Not every node is the same. A full node downloads and checks every block. An archive node also keeps every past detail forever, which is mostly done by services like block explorers. A light node keeps only the block headers and asks full nodes for the rest. The less you check, the more you trust others. > Check less, trust more. What does it take to run a full node? For Bitcoin, the full history runs to hundreds of gigabytes and keeps growing. But the software can prune old blocks once it has checked them, bringing it down to a few gigabytes. An ordinary desktop or laptop with a steady connection can do the job. > An ordinary computer can run one. And when a brand-new full node joins, it doesn't download a summary and trust it. It fetches every block from other nodes and checks each one, starting from the very first block and working forward. That first sync can take a long time. That's the price of trusting nobody. > Slow to start, because it trusts nobody. On Ethereum, a node runs two programs side by side. An execution client runs the transactions and keeps track of balances. A consensus client handles agreement on which blocks count. And there are several independent versions of each, written by different teams. > Several teams, several versions. Why several versions? If everyone ran the exact same software and it had a bug, the whole network could stumble at once. With different teams writing different versions, a bug in one doesn't take down everyone. It's the old rule: don't keep all your eggs in one basket. > Different teams, so one bug can't stop everyone. ## Who runs nodes? So who actually runs nodes? Exchanges, wallet companies and block explorers run them, because their business depends on it. The computers that produce blocks run them. And plenty of ordinary people run one at home. A plain node earns no block rewards. People run one to check the chain for themselves. > They run one to check for themselves. ## Your wallet asks someone Now the part that matters for your security. If you don't run a node, and most people don't, your wallet app still needs one. Every time it shows your balance or sends a transaction, it's talking to someone else's node. Your wallet only knows what that node tells it. > Your wallet knows only what the node tells it. And that node's operator can see a lot: which addresses your wallet asks about, and the internet address you're connecting from. Some wallet providers have said in their privacy policies that they can collect exactly this. Put together, that can tie your coins to your location. > Your IP plus your address can tie coins to your location. It's a bit like asking a clerk behind a window to read out your balance. They'll almost certainly tell you the truth. But now they know your account, what you look like, and what time you came in. Convenient, yes. Private, not really. > Someone else's node sees your activity. You do have options. Many wallets let you choose which node or provider they connect to. You can point your wallet at a node you run yourself, so your addresses never reach a stranger. And you can read your wallet's privacy settings before you trust it with a lot. Just know who you're talking to. > Know who your wallet is talking to. ## Careful with new networks And here's the security flip side. If a website or a message asks you to add a new network or change your wallet's node settings, slow down. Your wallet believes whatever node it's pointed at, so a node you can't trust is a source you can't check. So add networks only from your wallet's own built-in list, or from the project's official documentation that you typed or bookmarked yourself. Never from a pop-up on a site you just landed on, and never from a link in a message. Your wallet believes whatever node it's pointed at. > Your wallet believes whatever node it's pointed at. There's one more misunderstanding attackers love. Nodes don't hold your coins. Nobody who runs one can see your keys, freeze your wallet, or fix it for you. So a message saying your wallet needs to be resynced or validated with the network is fake. Real wallets sync with the network on their own, in the background. There's no step where you type your recovery phrase to fix a connection. Syncing never needs your phrase. Not once, not ever, no matter who is asking. > Syncing never needs your recovery phrase. ## Should you run one? So should you run your own node? You don't have to, and plenty of people never will. But if you hold a meaningful amount, or care about privacy, it's the most direct way to check the chain yourself instead of trusting someone else's word. Don't trust, verify. That's what nodes are for. > Don't trust. Verify. If you're curious, the path is simpler than people think. An ordinary computer, enough disk space, a steady connection, and the official software from the project's real website, typed in yourself. Let it download and check the history, which takes a while. Then point your wallet at it. Only ever get the software from the official site. > Get node software only from the official site. Step back and look at what all this adds up to. Thousands of independent computers, run by strangers who don't trust each other, all holding the same ledger and all checking the same rules. No headquarters to raid, no server to unplug, no single person to bribe. > No headquarters. No off switch. No one to bribe. ## Which block counts? But that raises a hard question. If thousands of strangers each hold a copy, and new blocks arrive from every direction, how do they all agree on which block comes next? What if two different blocks show up at the same moment? That's the problem of consensus. > Agreeing is the hard part. ## Who keeps the copies Here's the whole lesson in four lines. A node is a computer that keeps and checks the ledger. It trusts no one and checks every rule itself. Your wallet relies on someone's node, and that node can see your activity. And no node can hold, freeze or fix your coins. Don't trust. Verify. > Don't trust. Verify. ## Sources - [A full node fully validates transactions and blocks and relays them; pruning cuts disk use from over 750 GB to around 7 GB; minimum: a recent desktop or laptop, 2 GB RAM, steady connection](https://bitcoin.org/en/full-node?ref=cryptowithblock.com) - [Ethereum: a node runs an execution client and a consensus client; full, archive and light nodes; running your own node lets wallets avoid leaking addresses and balances to intermediaries; multiple client implementations reduce dependency on a single codebase; validators are an optional add-on](https://ethereum.org/developers/docs/nodes-and-clients.md?ref=cryptowithblock.com) - [Bitnodes estimate of Bitcoin nodes (reachable and unreachable) across 186 countries; described as a rough estimate](https://bitnodes.io/nodes/all/countries/90d?ref=cryptowithblock.com) - [Value overflow incident: August 15, 2010, block 74638, about 184.467 billion BTC created; patched client released within five hours; soft fork rejected the transaction; corrected chain overtook the bad one at block 74691 on August 16, 2010](https://en.bitcoin.it/wiki/CVE-2010-5139?ref=cryptowithblock.com) - [Bitcoin whitepaper: nodes accept a block only if all transactions in it are valid and not already spent](https://courses.csail.mit.edu/6.857/2015/files/L07-nakamoto-bitcoin-a-peer-to-peer-electronic-cash-system.pdf?ref=cryptowithblock.com) - [ConsenSys disclosed that Infura, MetaMask's default RPC provider, collects users' IP address and wallet address when they send a transaction; users can switch to another RPC provider](https://www.theblock.co/post/189717/consensys-says-it-collects-ip-addresses-of-metamask-users-via-infura?ref=cryptowithblock.com) *Education only. Not financial advice.*