Omnibus Account

An omnibus account is a custody arrangement in which many customers' assets sit together in wallets the platform controls, with each customer's share recorded only in the platform's internal ledger rather than in a wallet of their own. Almost every trading venue is built this way, because pooling is what makes instant internal transfers and order matching possible without an on-chain transaction for each one. The consequence is that your balance is a claim on a record, not a coin you can point to. On-chain you cannot distinguish your share from anyone else's, which is why an omnibus model makes proof of reserves and proof of liabilities the only external evidence available, and why it depends on the platform's accounting being accurate and its pooled wallets being segregated from its own funds. The alternative, a separate on-chain address per customer, makes ownership visible but costs a transaction and a fee for every internal movement, which is why it is usual in custody services and rare in exchanges.