AssumeUTXO

AssumeUTXO is a Bitcoin Core feature that lets a new node become usable in minutes by loading a snapshot of the Unspent Transaction Output set from a recent height, instead of validating every block from genesis first. The node syncs from the snapshot forward to the chain tip so a user can transact almost immediately, while quietly verifying the entire historical chain in the background.

How the snapshot is loaded

An operator supplies a snapshot created with the dumptxoutset RPC on an already-synced node, then imports it with loadtxoutset. Bitcoin Core builds a second chainstate from the snapshot and uses it to follow the tip, while the original chainstate continues validating from genesis. Once the background sync reaches the snapshot height and confirms it, full and equal trustless security is restored, matching a node that never used the shortcut.

The trust model

The integrity check rests on a snapshot hash hardcoded into Bitcoin Core's source and reviewed by developers, so a user is trusting the same code they already run rather than a third party. The feature first shipped in Bitcoin Core 26.0, with mainnet snapshot parameters for block 840,000 added subsequently. There is no canonical download host; any snapshot is verified against the in-source hash regardless of where it came from.

AssumeUTXO lowers the barrier to running your own validating node, a cornerstone of digital sovereignty. It is conceptually distinct from but often discussed alongside the UTXO set compaction work like Utreexo.