What is an Order Book?
An order book is a list of buy orders (bids) and sell orders (asks) for an asset, sorted by price. Exchanges use it to match buyers and sellers: when a bid price meets or exceeds an ask price, a trade is executed. The order book shows depth (how much size at each price) and the spread (gap between best bid and best ask).
How to Use This Simulator
- 1
Watch the ladder
Green bars are bids (buy orders), red bars are asks (sell orders). The chart updates as orders arrive and cancel.
- 2
Use Play / Pause
Pause to inspect the book; play to see continuous simulation of order flow and matching.
- 3
Adjust speed
Change the speed slider to see more or fewer simulated events per second.
- 4
Reset
Reset starts a fresh order book so you can observe the process from the beginning again.
Why Use an Order Book Simulator?
- Learn price discovery – See how bids and asks interact to form the last trade price and spread.
- Understand matching – When a new order crosses the spread, it matches with the opposite side and reduces depth.
- See cancellations – Orders are removed when cancelled, changing depth without a trade.
- Zero risk – Pure simulation in your browser; no real orders or data.