Order Book
Our perpetual futures markets use a central limit order book (CLOB). If you’ve traded on a centralized exchange, it’ll feel familiar
An order book is simply a live list of:
Buy orders (bids) - traders who want to buy at a given price
Sell orders (asks) - traders who want to sell at a given price
When a buy and sell order are compatible, they can match and trade.
How the order book works
Price levels and tick size
Orders can only be placed at prices that align with the market’s tick size.
Tick size = the smallest allowed price increment
Example: if tick size is 0.5, valid prices are 100.0, 100.5, 101.0, etc.
This keeps the book organized into clean price levels.
Order size and lot size
Order sizes must align with the market’s lot size.
Lot size = the smallest allowed size increment
Example: if lot size is 0.001 BTC, valid sizes are 0.001, 0.002, 0.003 BTC, etc.
How matching works (price-time priority)
Orders are matched using price-time priority, which is the standard for most order-book exchanges.
Price priority: better prices fill first
For buys: higher price is better (higher bids match first)
Example: a bid at $101 will fill before a bid at $100
For sells: lower price is better (lower asks match first)
Example: an ask at $99 will fill before an ask at $100
Time priority: earlier orders fill first (at the same price)
If multiple orders are placed at the same price level, the order that was placed first is first in line.
Example: if two buy orders are both placed at $100, the one submitted earlier will fill first.
Maker vs taker
When a trade happens, it’s typically one of these:
Maker: your order rests on the order book and provides liquidity
Taker: your order fills immediately against existing liquidity
Whether you are maker or taker can affect your trading fees.
What happens during a fill
A single order can be filled:
Fully (entire size executed), or
Partially (some executes, the rest stays on the book)
If your order is partially filled, the remaining size keeps its original time priority at that price level.
Quick glossary
Bid: a buy order on the book
Ask: a sell order on the book
Spread: the difference between best ask and best bid
Tick size: minimum price increment
Lot size: minimum size increment
Price-time priority: best price first, then earliest order