Monero's November 2025 network upgrade implemented a long-anticipated increase in the protocol's default ring size — the number of decoy inputs included in each transaction — from 11 to 16. This change, which activated at block height 3,414,209, directly improves the anonymity guarantees of every Monero transaction on the network.
Ring signatures are one of Monero's three core privacy mechanisms. When sending XMR, the sender's real input is "mixed" with a number of other outputs from the blockchain as decoys. An observer cannot determine which of the ring members is the actual spender. The larger the ring, the lower the statistical probability of correctly identifying the real input.
Privacy Impact
With a ring size of 11 (the previous standard), the theoretical probability of correctly guessing the real input — assuming uniform random decoy selection — was approximately 1/11 or 9.09%. With a ring size of 16, this drops to 1/16 or 6.25%. In practice, sophisticated decoy selection algorithms and the interaction effects between multiple transactions make the real-world privacy guarantees significantly stronger than these naive probabilities suggest.
Researchers analyzing the change noted that increasing ring size also increases resistance to intersection attacks — where an adversary observes the same output appearing in multiple rings and uses set intersection to narrow down possibilities. A larger ring requires observing more transactions before intersection attacks become statistically meaningful.
For Nexus users, the change is automatic — all XMR transactions made after the activation block benefit from the larger anonymity set without any action required. The fee impact is minimal: each additional ring member adds approximately 3-4 bytes to transaction size, resulting in roughly 2% higher fees — a negligible privacy-cost tradeoff.