In one-way mode, you can only hold positions in one direction under one contract.
For example, if you open a short position and anticipate that the price will go down in the longer timeframe, but in the meanwhile, you also want to open a long position for a shorter time frame, you won’t be able to open positions in both directions at the same time. Opening positions in both directions would result in canceling one another out.
In hedge mode, you can hold positions in both long and short directions simultaneously under the same contract.
For example, you can hold both long and short positions of the BTCUSDT contract at the same time.
Please note that the old version of the trading interface is unable to support hedge mode and you need to switch to the latest version. For more information, please refer to How to Enable Hedge Mode.