A full node is a Bitcoin node that downloads every block since the genesis block in 2009 and checks every rule for itself. It trusts no one. It verifies everything.
What it verifies
For each block and transaction, a full node checks that the proof of work is valid, that no coin is spent twice, that every digital signature is correct, that the block reward is not too large, and that the difficulty is correct. If anything is off, it rejects the data, even if every miner in the world produced it.
Initial block download
When you start a new full node, it downloads and validates the whole history, about 780 GB as of October 2026. Depending on your hardware and internet connection, this takes from a few hours to a few days. After that, keeping up with new blocks is light work.
Pruned nodes
You do not have to keep every old block. A pruned node validates everything from the beginning but then deletes old block data, keeping only recent blocks and the UTXO set. It typically needs only around 10–15 GB of storage in total and is just as secure in its verification.
Why run one?
Trust nothing: you verify your own payments instead of trusting someone else's server.
Privacy: your wallet asks your own node about your addresses instead of revealing them to a third party.
A voice in the rules: nodes enforce consensus. The more people run full nodes, the harder it is for anyone to change Bitcoin's rules without users agreeing.
What you need
A spare computer or a small dedicated device, a 1–2 TB SSD, and a stable internet connection. Free software like Bitcoin Core, or plug-and-play node packages, can make it easy. Many people consider running a node the final step of self-custody.