Spread

The spread is the difference between the best bid (highest buy order) and the best ask (lowest sell order) for a trading pair. It is the implicit cost of trading instantly: buy at the ask, and you would have to sell at the lower bid to exit, losing the spread even if the price does not move.

For example, if BTC/USDT shows a best bid of $60,000 and a best ask of $60,020, the spread is $20, or about 0.03%. On a major pair at a large exchange the spread is typically tiny; on a thinly traded altcoin pair it can be several percent, which makes frequent trading expensive before fees are even counted.

Spreads widen when volatility spikes or liquidity dries up, because market makers pull their quotes to avoid being run over. A common beginner mistake is to focus only on exchange fees while ignoring spreads: a platform advertising "zero fees" can still be expensive if its spreads are wide, since that cost is baked into the prices you trade at.