Quick answer
The spread is the difference between the best available buy price and the best available sell price.
What is Spread?
In an order book, the bid-ask spread is the gap between the highest visible bid and the lowest visible ask. It is one simple indicator of immediate trading friction, not a complete measure of market quality.
The useful way to approach this term is to separate its definition from the assumptions people often attach to it. In crypto, the same word can appear in a protocol rule, a user interface, a market-data label, or a marketing claim. Check which layer the explanation is describing.
Why does spread matter?
A wider spread can increase the cost of entering and exiting, particularly for smaller or less liquid assets. Comparing the spread across venues can reveal different execution conditions.
Concrete example
See it in a real situation
If the highest bid is $99.90 and the lowest ask is $100.10, the displayed spread is $0.20 before fees and slippage.
Common misconceptions
What this term does not mean
- The spread is not the same as the exchange’s published commission.
- A narrow spread at one moment can widen quickly during volatility or low activity.
Related terms
Sources and further reading
Definitions are written for education and checked against the sources below where relevant. A source can explain a protocol or rule without endorsing every product built around it.