Is crypto Convert really free if it shows a 0% fee?

Why a 0% fee is not a 0% cost

A spot order is matched against other traders on the order book, and the exchange charges a maker or taker fee on top, shown as its own line. Convert works differently. OKX's help center says Convert uses a quoting model instead of the order-matching model of spot trading, isn't matched against an order book, and doesn't charge a separate trading fee or use the spot maker and taker fees. Instead, a Convert quote includes a spread, so a conversion can return less than the spot price suggests even when no fee is displayed.

The other exchanges describe the same model in their own words:

• MEXC launched Convert as having no trading fees, with exchange rates determined by current market conditions and conversions usually done at a fixed quoted rate.
• BingX's Convert FAQ says the trading fee is 0% and that the rate is a composite derived from its own trading volume, rates from several spot exchanges and market depth — data it calls "for reference only", with the actual result prevailing. An older BingX how-to from 2020 lists a small handling fee instead, so the two pages don't agree; the preview screen is what counts.

What moves the spread

OKX lists three things the quote reflects: the size of the conversion, current volatility, and the liquidity available for the two assets at that moment. The spread isn't fixed. In practice that means:

• A large conversion of a thinly traded token costs more, in percentage terms, than a small conversion between major coins.
• A quote taken during a sharp move is wider than one taken in a quiet market.
• The quote is only valid for a short time before it refreshes, and OKX notes that the amount shown before you confirm is an estimate — settlement uses the rate at execution.

How to measure what a conversion cost you

1. Before confirming, note the amount the preview says you'll receive.
2. Look up the current spot price of the same pair on the same exchange.
3. Work out what the same amount would buy at that spot price. The gap between the two, as a share of the spot value, is your conversion cost.

Then compare it with the alternative: a spot order pays a visible maker or taker fee (see maker vs taker fees) and, with a market order, some slippage (slippage vs trading fee). OKX's own advice is to consider spot trading for larger amounts, where you can set the price you're willing to accept. For a small, one-off swap, Convert's simplicity may be worth a slightly worse rate; for regular or large conversions, the spread adds up quietly because it never appears in your fee history.

Does Convert earn a fee rebate?

A fee rebate is a share of the trading fees you actually pay, so it only exists where a fee is charged. A Convert trade with no fee line leaves nothing to share, and the spread is part of the price, not a fee — it is never rebated. Trades on the order book do pay a fee; which of those products an exchange counts toward its affiliate commission is set by its own program, and rebates are calculated from the commission the exchange reports. If keeping costs down matters to you, the trades that benefit from a rebate are the ones where a fee is charged — see what a fee rebate is and ways to reduce trading fees.