What execution quality means
Good execution quality usually means:- your order filled quickly enough for the trade idea
- the average fill stayed reasonably close to the expected price
- the order behaved the way the chosen order type was supposed to behave
- the order filled worse than expected
- the order filled only partially
- the order stayed in the book longer than the trader expected
- the market moved through a thin area and the average fill became less efficient
Slippage
Slippage is the difference between the price you expected to trade at and the average price you actually received. This happens because the market can move or because your order consumes more than one price level in the book. Slippage usually increases when:- the book is thin
- volatility is high
- your order size is large relative to visible liquidity
- you use a market order during a fast move
Partial fills
One order does not always fill as one clean block. If there is not enough liquidity available at one level, the order can fill in pieces. This is a partial fill. That can happen with:- market orders, if the order walks through several price levels
- limit orders, if only part of the resting size gets matched
- the position may open in stages
- the average entry price can change while fills are coming in
- the remaining unfilled size may stay active in the book
Queue position
When a limit order rests on the book, price alone is not the whole story. Queue position matters too. If many orders are already waiting at the same price:- earlier orders usually get matched first
- your order may remain open even though the market traded at your level
- a touch of your price does not always mean your full size will fill
Maker and taker outcomes
Execution quality also depends on whether the order adds liquidity or removes it.- Taker behavior usually means faster execution, but often with more slippage and higher fees
- Maker behavior usually means more price control, but with slower or uncertain execution
- a market order is usually taker flow
- a resting limit order is usually maker flow
- a limit order can still behave like a taker if it crosses the current spread and executes immediately
Thin order book behavior
Thin markets are where execution quality matters most. When the order book is thin:- small aggressive orders can move price faster
- market orders can jump through multiple levels
- spreads can widen
- exits can become less precise
Choosing the right order type for the conditions
Use a market order when:- getting filled now matters more than precision
- you need to close risk quickly
- price control matters more than speed
- you are comfortable waiting in the queue