How Post Only actually works on MEXC ETHUSDT perps, and where it sits next to Limit, Market, Trigger and Chase Limit (Beginner)

Post Only is a limit order with one extra rule: if it would trade immediately, MEXC cancels it instead. The result is that it can only ever enter the book as a maker order. On the ETH_USDT perpetual, where MEXC's contract data lists a 0% maker fee and a 0.02% taker fee, that rule is worth understanding before anything fancier.

The image is the live MEXC ETHUSDT perpetual page from this morning: 15m chart, order book, and the order panel on the Limit tab, with Market and Chase Limit Order next to it and Last / BBO price buttons.

1. Know the contract

MEXC public API, this morning: 1 contract = 0.01 ETH, minimum 1 contract, price tick 0.01, max leverage 500x, one order up to 70,000 contracts (700 ETH). Last 2,319.99, fair price 2,319.98, index 2,320.78, 24h range 2,296.53 to 2,343.79.

1. Read the book before choosing

In the screenshot the best ask is 2,318.61 and the best bid 2,318.60. A Post Only buy at 2,318.61 or higher would match the ask, so it is cancelled. A Post Only buy at 2,318.60 or lower rests in the book and waits.

1. Count the fee gap

1 ETH = 100 contracts. At 2,319.99 that is 2,319.99 USDT notional.

• Market (taker) entry: 2,319.99 x 0.0002 = about 0.46 USDT
• Post Only (maker) entry: 0 USDT
• Market in and out: about 0.93 USDT; maker both ways: 0

1. Know what Post Only does not promise

MEXC's own FAQ is clear: it guarantees maker status, not a fill. Price can walk away and leave you with nothing. MEXC also warns against using it for urgent stop losses, because a stop that gets cancelled or never fills is worse than a taker fee.

1. Place it next to the other tabs

• Limit: your price or better; can fill at once or rest.
• Market: fills now at the best available price; slippage possible.
• Trigger: waits for a trigger price, then places your preset order. MEXC notes no margin is frozen before it triggers, and a triggered limit can still miss.
• Trailing stop: follows price by a set distance before firing.
• Chase Limit: a limit order that keeps re-pricing to the best bid or ask until filled, cancelled or the max chase distance is hit. Hedge Mode only.

1. Same steps, other pairs

BTC, SOL, XRP and DOGE perps use the same tabs; check each contract's size and fee line first.

Takeaway: Post Only buys you the maker rate by giving up the guarantee of a fill, so use it when you can wait and never when you need out.