Market order
An order to buy or sell immediately at the best available price. Guarantees execution but not price — especially risky on a thin market.
Aliases: market buy, market sell
Market order is a request for immediate execution at whatever price is currently available. On AMM-based DEXs, a “market” trade is just a swap: the contract derives the output from the pool formula.
Execution guaranteed, price not
The defining property: the trade will fill as long as the source has enough volume. Price is a function of depth, order size, and the current book / pool state.
Order-book example, BTC/USDT:
99,990 — 0.1 BTC
99,985 — 0.3 BTC
99,980 — 1.0 BTC
99,975 — 5.0 BTCA 2 BTC market order eats 0.1 + 0.3 + 1.0 + 0.6 BTC across those levels; average fill ~99,982. The thinner the book, the worse the average.
Market order on an AMM (TON DEXs)
On STON.fi, DeDust, and most AMM DEXs the market order is not split across levels — it slides along a curve. The contract says “send Δx, receive Δy” where Δy = f(reserves). All swaps are market orders by default; the AMM core has no limit concept (limit orders are a separate primitive run by keeper bots).
When to use market
- Execution urgency. Price is moving and the risk of missing fills outweighs a few basis points of slippage.
- Small size vs liquidity. A 100-USDT trade against a million-USDT pool has negligible slippage.
- Tight pricing is not critical for the strategy.
When limit is better
- Trade size is comparable to depth — market would give a bad average.
- No urgency.
- You want to control the worst-case fill.
Market on perpetuals
On a perpetuals DEX a market order opens a position at mark price plus spread. Fine on small size; large positions deserve splitting or a limit.
Market orders are the simplest tool — and the one that most often costs users 0.5–2% to slippage and MEV. If size matters, spend the five seconds to use a limit.