Best Bid and Offer (BBO)

What Is the Best Bid and Offer?

The Best Bid and Offer (BBO) represents the tightest available quote on a single exchange, consisting of the highest bid price and the lowest ask (offer) price currently posted. The BBO is the "top of book," showing the best prices at which a trader can immediately buy (at the ask) or sell (at the bid) on that particular venue.

The spread between the best bid and best offer is the tightest the market is currently offering on that exchange. All other limit orders rest at less favorable prices, forming the depth of the order book below the BBO.

BBO in the Multi-Exchange Landscape

In the US, securities trade simultaneously on multiple exchanges (NYSE, NASDAQ, CBOE, IEX, and many others). Each exchange has its own BBO based on the orders resting on its book. The NBBO (National Best Bid and Offer) aggregates all exchange BBOs to find the absolute best bid and absolute best ask across all venues.

Because orders can be split across many exchanges, the BBO on any single exchange may not represent the best available price nationally. Regulation NMS requires that trades be executed at the NBBO or better, ensuring that traders receive the best available price regardless of which exchange their order is routed to.

BBO and Trading Decisions

For market order execution, the BBO (or more precisely, the NBBO) determines where execution begins. Market buy orders fill at the national best offer; market sell orders fill at the national best bid. Understanding the BBO helps traders estimate their likely fill price.

For limit order placement, the BBO provides context. A limit buy order placed above the current best bid has a higher chance of filling quickly but adds to one side of the spread. A limit order placed at a price inside the spread (between the bid and ask) may capture a better price if a counterparty arrives.

Quote data providers deliver BBO information in real time. Level 1 data shows the BBO, last trade, and basic statistics. Level 2 data shows the full order book beyond the BBO, revealing the depth of supply and demand at multiple price levels.