Gemini operates three distinct order matching engines, one for each of our trading pairs—BTC/USD, ETH/USD, and ETH/BTC. Customers may submit orders to any of the three matching engines at any time. Our marketplace operates 24 hours a day, seven days a week (except for brief maintenance periods).
Customers may submit as many orders as they want of the types described below. Because Gemini is a full reserve exchange, we require that all trades be pre-funded (i.e., assets must be on deposit in your account before attempting to trade them). All open orders reduce customers’ available balance until the orders are fulfilled or canceled.
Beginning Wednesday, September 21, 2016, we will begin conducting two-sided Auctions at 4:00 p.m. Eastern Time every day in BTC/USD. Auctions in other trading pairs will be enabled at a later date. Check out our Auction Data page to see the results of Gemini’s previous auctions.
Our order matching engine currently supports six order types, as described below.
- Market—filled immediately against resting orders.
- Limit—filled at or more favorably than the specified price against resting orders. If some of the quantity remains unfilled, it rests on the continuous trading order book until traded against.
- Immediate-or-Cancel (IOC)—similar to Limit Order, filled immediately at or more favorably than the specified price against resting orders. Any remaining quantity is immediately canceled and does not rest on the continuous trading order book.
- Maker-or-Cancel (MOC)—similar to Limit Order, rests on the continuous trading order book at the specified price. However, if any part of the order can trade against resting orders, it is immediately canceled instead.
- Auction-only (AO) market—attempts to be filled at any price only during the Auction.
- Auction-only (AO) limit—attempts to be filled at or more favorably than the specified price only during the Auction.
|Specifies Price||Trades Against Resting Orders||Can Rest on Continuous Trading Order Book||Can Trade in Auction|
|Auction-Only (AO) Market||Yes|
|Auction-Only (AO) Limit||Yes||Yes|
For each trading pair, we offer a continuous trading order book. This allows for continual interactions between market orders and limit orders. Limit orders interacting with the order book may additionally carry one of two options (see below).
Customers who wish to trade immediately may enter market orders to buy or sell. Because these orders do not specify a price constraint, they may be fulfilled at any price or a variety of prices by orders already resting on our limit order book (see below). For ease of use, market orders to buy must specify a total notional value to convert from one asset to another (e.g., buy $100 worth of bitcoin), from which appropriate trading fees are first deducted. Market orders to sell must specify a total quantity of asset to sell (e.g., sell 5 BTC for USD); appropriate trading fees are deducted from the proceeds. For a more detailed discussion of fees, please see Trading Fees & Rebates.
As with most other marketplaces, customers may also place limit orders to buy or sell. These orders might not trade immediately if no other customer is willing to trade at the specified limit price (or better). Any untraded quantity rests on our order book until fulfilled by incoming eligible orders. Thus, a limit order might not immediately be fulfilled; trades depend on interactions with other marketplace participants. Customers may attempt to cancel orders while they rest on the order book. The quantity and limit price are specified separately from fees. (Gemini does not currently allow limit orders to be “replaced” or “amended;” customers must enter an entirely new order to specify a different limit price or quantity.)
Our marketplace also allows limit orders to be entered with one of two order options: immediate-or-cancel (“IOC”) or maker-or-cancel (“MOC”). IOC orders are common on other marketplaces. This option specifies that a limit order should not be allowed to rest on the order book; instead, any quantity not executed immediately is canceled. MOC specifies the opposite: if the limit order would trade immediately against an eligible resting order, it is instead canceled. MOC orders only trade after first resting on the order book. In summary, all trades from IOC orders are liquidity-taking, and all trades from MOC orders are liquidity-making.
Priority of Orders Book
Limit orders resting on our book are sorted by price-time priority. That is, if an incoming market or limit order could be fulfilled by multiple resting limit orders, eligible orders at the most favorable price are considered first (i.e., lowest resting sell orders for an incoming buy or highest resting buy orders for an incoming sell). If multiple limit orders are resting at the same price, those which were placed earlier are considered before those which were placed more recently. Partially filled resting limit orders keep their priority until canceled.
In addition to the continuous trading order book, each of the order matching engines conducts an Auction (or “cross”) at 4:00 p.m. Eastern Time (i.e. 21:00 UTC during the winter and 20:00 UTC during the summer in New York) every day. This provides an opportunity for both buyers and sellers to trade in an instant of elevated liquidity and price discovery. All active orders (including resting limit and MOC orders) may interact with the Auction and influence the final auction price, which is determined by finding the price at which the greatest aggregate buy demand and sell demand are fulfilled. All participating, eligible orders are fulfilled at the final auction price. (We use a mechanism similar to the New York Stock Exchange’s Arca marketplace, Nasdaq, Bats, and other large stock exchanges throughout Europe and Asia, which is sometimes called Walrasian equilibrium.)
Customers may enter both market orders and limit orders as auction-only, indicating that they will not take part in continuous trading (as described above) but instead only become eligible to trade at the time of the Auction. Customers may submit as many auction-only orders as they want for a particular Auction, provided all orders are pre-funded. If not all eligible orders can be fulfilled during the Auction (which can occur when demand on one side of the market outweighs demand on the other), they will be given priority based on receipt time. If an auction-only limit order cannot be satisfied by the final auction price, it will be canceled back to the customer after the completion of the Auction. Beginning at 5:00 p.m. ET, auction-only orders will be accepted for the next day’s Auction. Auction-only orders may be canceled up until 3:59 p.m. ET; after that time, they’re locked in to the 4:00 p.m. Auction.
The final auction price of each Auction is determined by finding the price at which the greatest aggregate buy demand and sell demand from all eligible orders are fulfilled; all continuous trading book orders and auction-only orders are considered. (In the event of a tie between multiple prices, the midrange is used.) Beginning at 3:50 p.m. ET, indications of the upcoming auction price are broadcast via both our market data API (see below) and the website UI. (In order to calculate these indications, we simulate the auction process for the order books at that time.) These indicative auction prices are updated every 60 seconds leading into the Auction. In general, these indications should converge on the final auction price and should also provide guidance for prices on the continuous trading order books.1 If the matching engine cannot converge on an effective2 final auction price, the Auction will be canceled, all auction-only orders will be canceled back, and all continuous trading book orders will be unaffected.
Check out our Auction Data page to see the results of Gemini’s previous auctions.
All trades on our marketplace are reported both to the customer and to the public via our market data API. The summed quantity of limit orders (only standard and MOC) resting at each price level throughout our three order books is also publicly available via our market data API. Additionally, the value of each digital asset is determined by the most recent trade (sometimes called last price) executed by the relevant matching engine; this convention is called “marking to market.” All Account Balances on Gemini are marked to market.
2 The matching engine requires that the final auction price differ from the midpoint of the continuous trading order book at the time of the Auction by no more than 5 %.