US state regulators publish monthly handle and revenue figures, which is why handle is the industry's headline growth metric; single events like the Super Bowl generate billions in nationwide handle. For bettors the concept mostly matters as context: high-handle markets are liquid, tightly priced, and slow to offer value; low-handle markets are where prices wander.
Handle is reported by books and regulators, not carried in odds feeds. Its practical proxy in the feed is market density: how many books quote a market, how tight the overround is, and how quickly prices converge after news - all directly observable across ParlayAPI's aggregated books.