The Unique Node List (UNL), the consensus mechanism behind the XRP Ledger cryptocurrency.
It's the method by which XRP agrees on transactions: each participant picks a list of trusted validators to rely on.
Unlike Bitcoin-style proof-of-work or proof-of-stake, XRP's default trusted-validator lists are curated centrally by Ripple and the XRPL Foundation, and that central curation is exactly what gives the network its speed and efficiency — at the cost of true decentralization.
It shows XRP buys operational efficiency by keeping the trusted-validator list under central control. That central curation is the structural trade-off that limits its independence from its founders.