The data tracked by MetaMage is exclusively Best-of-3 (BO3). All MTGO sources are Challenges, Qualifiers, and similar competitive events which run BO3 match play. Melee events are similarly competitive paper tournaments that use BO3. BO1 queues on MTGO are not tracked.
Looking at the last 30 days specifically, the data comes from 91 tournaments: 54 MTGO events (59%) and 37 Melee paper events (41%). Every one of those events uses BO3, so all match results, winrates, and metagame shares you see from MetaMage reflect BO3 play exclusively.
Sources: Data from 91 tournaments over the past 30 days (59% MTGO, 41% Melee). Example events: Modern RC Super Qualifier (2026-10-03, https://www.mtgo.com/decklist/modern-rc-super-qualifier-2026-10-0312855444), Modern Challenge 16 (2026-10-03, https://www.mtgo.com/decklist/modern-challenge-16-2026-10-0312855475).