Wash Trading
Trading with yourself, or with a partner, to create the appearance of activity without any real change of ownership.
Motives are straightforward: rank higher on volume tables that drive listings and attention, qualify for token rewards paid per unit traded, or manufacture a price history for an illiquid item. Detection relies on patterns such as matched buys and sells between related accounts, round trips that return an asset to its origin, trades priced far from the market, and clusters of addresses funded from the same source. Venues with zero fees or trading incentives make the practice nearly costless, and on-chain marketplaces are exposed too because one person can control both sides with different addresses. Data providers respond by publishing adjusted volume that excludes venues failing their tests, which is why two reputable sources can show very different volume for the same asset. In regulated markets the practice is illegal in many jurisdictions.
En pratique
Marketplace sale histories can be inflated when the same person controls the buying and selling addresses, producing recorded sales with no change in beneficial ownership.
Le malentendu courant
Wash trading is not only an exchange problem; on-chain marketplaces record it just as readily, because addresses are free and one person can control both sides.