The mechanics
The scheme is simple: swap a dollar for coin A, coin A for coin B, coin B back to dollars. All three trades happen on one venue, so nothing is transferred, networks and withdrawal fees play no part, and the whole thing takes seconds.
That is exactly the appeal: no transfer means none of the main risk of cross-venue arbitrage, where price moves while the coin is in flight.
Trap one: which price to use
A book is not symmetric. Selling a coin gets you the bid; buying it costs you the ask. The difference between them is the spread.
Many scanners use the mid price because it is easier. On one leg the error is small, but there are three legs here, and the overstatement comes to roughly one and a half spreads. On pairs where the spread is hundredths of a percent, that is precisely the magnitude separating a profitable triangle from a losing one. So our scanner prices each leg from its own side of the book.
Trap two: size
This is the big one. A triangle is executable exactly as far as the best order in each of the three books goes. On a dead pair a "5% triangle" can mean an order for two dollars.
How serious this is shows in the numbers. Testing OKX we found a triangle showing 85 percent with an executable size of zero dollars: one leg had an order against which nothing could be bought. KuCoin's four best triangles were the same illusion.
So executable size is computed and shown next to every triangle, and anything under a hundred dollars is discarded: three trades for two cents are worth neither the fees nor the risk.
Why the fee decides everything
Triangles on major venues live between one and five hundredths of a percent. Three trades at the usual 0.1% cost 0.3% — several times the opportunity.
The conclusion is worth accepting before you start: at standard taker fees, triangular arbitrage on Binance, Bybit, OKX, KuCoin and Bitget does not work today. No triangle covers the cost. The market is efficient and whatever appears is taken by bots within fractions of a second.
It can work in two cases. First, at zero or near-zero fees: MEXC's spot maker tariff is zero, and there triangles worth hundredths of a percent stay positive. Second, with maker execution, where you earn the spread instead of paying it — but a resting order still has to fill, and the other leg moves while you wait.
What to remember
- Price each leg from its own side of the book, never the mid.
- Look at executable size before you look at the percentage.
- Multiply your fee by three and compare it with the gross return.
- At a 0.1% fee a triangle must beat 0.3% — none do today.