What is a limit order? How it works in crypto trading

1. Definition of limit order

A buy limit order specifies the highest acceptable bid price, and a sell limit order specifies the lowest acceptable ask price.

• Buy limit price: Transactions can only be made at the limit price or lower.
• Sell limit price: Transactions can only be made at the limit price or higher.

Let’s say ETH is quoted at $3,000. If you submit a limit order of "Buy 1 ETH for $2,900," the system will not automatically increase the price to $3,000 in order to fill the order as quickly as possible. Conversely, if the market drops quickly to $2,880, the order may be filled at $2,900 or more, with the actual price being filled depending on the order book.

Limit orders control price boundaries, not precise results. The same order may be completed all at once, or it may be split into multiple orders, or even not completed for a long time.

2. Order book and matching sequence

Centralized exchanges and on-chain trading venues that use order books usually follow "price first, time first" matching. The higher the buyer's quotation and the lower the seller's quotation, the closer they are to being completed; orders with the same price are usually sorted according to the order in which they are entered into the order book.

Suppose the selling order is as follows:

If you submit a limit order of $80,050 to buy 0.6 BTC, you can theoretically eat $80,000 of 0.2 BTC first, and then trade $80,050 of 0.4 BTC. But actual results are also affected by orders arriving at the same time, matching delays, fees and trading venue rules.

If you set the buy limit price above the current ask price, the order may be filled immediately. It's still a limit order, but your price range already covers the existing sell order. Some platforms refer to this behavior as "tradable limit orders".

3. Maker, Taker and Fees

Limit orders are not always Maker orders. Only when an order enters the order book first, adding tradable depth to the market, it is usually considered a Maker; if the limit price covers the existing counterparty order and is filled immediately, it may become a Taker.

This will affect the handling fee. Some platforms charge lower rates to Makers and even offer rebates in certain markets; Taker fees are usually higher. If a trader only looks at the limit price and ignores the fee rate, he may find that the actual cost is much higher than expected after placing frequent orders.

“Post Only” can be used to avoid orders being taken immediately. Once enabled, if an order would immediately become a taker, the system will usually cancel or reject it. However, the processing methods of different platforms are not exactly the same, so you should check the rules before placing an order.

4. Why the order may not be filled even though the price has been hit

Just because a certain price has appeared on the chart, it does not mean that your order must have been placed. Common reasons include:

1. The market has only executed a small amount at that price, and your order is ranked behind the earlier pending order.
2. The chart uses the latest transaction price, index price or mark price, while the order trigger relies on another price.
3. The price quickly skips this level, and the quantity that can be traded is insufficient.
4. The order is set with the wrong trading pair, network, direction or expiry date.
5. The order is not accepted due to the platform’s minimum quantity, price step size or risk control rules.

When observing limit orders, you cannot just look at the lowest point or highest point of the K line. More useful information is deal details, order status, remaining quantity, and order book depth.

5. Validity settings for GTC, IOC, FOK, etc.

Different validity periods determine how the order is processed when it is not fully filled.

Not all platforms offer the same options. On-chain orders may also be affected by block confirmations, oracle updates, gas, and smart contract status.

6. What scenarios are limit orders suitable for?

Limit orders are suitable for people who have clear requirements for entry or exit prices and are willing to wait. For example, buy in batches in a pre-defined support area, or gradually reduce your position in a target area.

It is also suitable for controlling the average transaction price of large orders. Splitting a large order into multiple price brackets can reduce the impact of eating through the order book in one go. However, splitting orders does not guarantee that the cost will be lower; if the market operates unilaterally, the unfilled portion may miss the transaction.

For users using OneKey Perps or other on-chain trading venues, limit orders can become part of the execution plan: first define the entry or exit price, then check for liquidity, fees, positioning and liquidation distance. After confirming the price boundary, you still need to check the leverage and maximum loss.

7. Common ways of failure

Treat limit price as stop loss

A normal sell limit is usually placed above the current price and is used to sell at a higher price. To exit after a price drop, you often need a stop loss market price or a stop loss limit price. Setting the wrong direction can make an order completely fall short of expectations.

Putting the price too far for the sake of “cheapness”

The price is attractive, but the market never reaches it, and the opportunity cost is also a real cost. The limit price should come from the trading plan, not just randomly fill in an integer below the current price.

Ignore partial transactions

Partial trades may leave a smaller position than planned and may also leave remaining orders that have not yet been cancelled. After the transaction is completed, the transaction quantity and pending order status should be checked.

Long-term forgotten pending orders

The market background, account balance, or trading logic has changed, but the old order remains in the order book. GTC orders need to be reviewed regularly, especially before major data releases, token events, or periods of high volatility.

8. Checklist before placing an order

1. Are the trading pairs and buying and selling directions correct?
2. Does the price limit come from a clear plan or a temporary guess?
3. Can the order book accommodate the planned quantity?
4. Are partial transactions allowed? How should the validity period be set?
5. What are the Maker/Taker fees, funding rates and on-chain fees?
6. How big is the position after the transaction is completed, and where is the stop loss or failure point?
7. If there is no transaction, when will the order be canceled or re-evaluated?

A limit order is an execution tool. It avoids paying any price for speed, but it cannot judge whether the trade direction is correct, nor can it replace position management.

9. A complete limit execution example

Assume a trader is prepared to buy when ETH falls back, and the account allows a maximum loss of 120 USDC on this trade. The planning area is 2,950 to 3,000, with trading assumptions breaking down below 2,880.

Rather than peg the entire quantity at one price, he divided it into three buckets: 3,000, 2,975 and 2,950. This can reduce the impact of single-point judgment, but it will also bring about partial transactions. If only the first tranche is traded, the stop loss should be set based on the actual amount of the position and cannot still be calculated based on the profit target of the full position.

Before placing an order, you also need to answer: If the price rises directly from 3,010, should you pursue the price? If all three positions are traded, what is the average price and maximum loss? If only one order is executed, how long will the remaining orders be kept? If important data will be released in two hours, should I cancel the order in advance?

This type of question is more important than "what is the price limit?" The limit order is responsible for execution according to conditions, and the complete plan is responsible for handling no transactions, partial transactions and market background changes.

10. The difference between centralized order book and chain price limit

Centralized exchanges usually match orders in internal order books, and order status is maintained by the platform database. On-chain price caps may be hosted by smart contracts, monitored by executors for conditions, or triggered by oracle prices. Different designs affect whether funds are locked, who pays gas, when orders expire, and how execution failures are handled.

On-chain orders also need to check the authorization limit. Granting unlimited token authorization for placing orders will exchange execution convenience for greater contract risk. Minimum necessary authorizations can be used and checked and revoked when the agreement is no longer used.

References

1. Phantom, Limit Orders: https://phantom.com/learn/crypto-101/limit-order
2. Investor.gov, Types of Orders: https://www.investor.gov/introduction-investing/investing-basics/how-stock-markets-work/types-orders
3. CME Group, Order Types: https://www.cmegroup.com/education/courses/introduction-to-futures/types-of-orders.html
4. OneKey Blog, OneKey Perps Full Asset Trading Guide: https://onekey.so/blog/zh-CN/learn/onekey-perps-all-asset-trading-guide/

Disclaimer

This article is for educational purposes only and does not constitute investment advice. Crypto-assets and leveraged products are highly volatile, and orders may be unfilled, partially filled, slippage, liquidated or have technical failures. Please make independent judgment based on your own risk tolerance.