Market Order

A market order is an instruction to an exchange to fill a trade immediately against whatever buy or sell orders are already sitting in the order book, rather than waiting for a specific price to be reached. The trader gives up control over the exact fill price in exchange for speed: the order matches the best available bid or ask first, then works down through the next-best price levels until it is fully filled or cancelled.

Because a market order removes existing liquidity rather than adding to it, exchanges classify it as a "taker" order and usually charge a higher fee than for a resting limit order. On deep, high-volume pairs such as BTC/USDT this cost is negligible, since enormous size sits within a fraction of a percent of the current price.

The real danger appears on thinly traded coins. If only a small amount of volume is available near the current price, a market order can "walk the book": the first portion fills near the expected price, but the rest is matched against progressively worse offers. This gap between the expected and actual execution price is called slippage, and it can be severe during flash crashes, low-cap pumps, or outside normal trading hours when order books are shallow.

• Best used on liquid pairs where near-instant execution is worth more than price precision.
• Risky on illiquid altcoins, where checking order book depth first, or using a limit order instead, avoids paying far above (or receiving far below) the visible market price.
• Many exchanges let traders set a maximum slippage tolerance to automatically cancel a market order if the price moves too far.