Why demo fills look better than live ones
Posted: Sat Oct 31, 2026 8:21 am
On many setups, a demo server fills at the quoted price almost instantly, with no re-pricing, no rejections, no partial fills and no meaningful slippage, even in the middle of a news spike. Liquidity looks unlimited because nothing real stands behind it. Live orders go to liquidity providers who may re-price, fill partially, or decline. Exact behaviour differs by broker, but the direction of the gap is nearly always the same.
For a swing trader this barely matters. For a scalper with a 3 pip target, 0.3 pip of extra slippage on both sides is 20 percent of the gross target.
Demo is useful for checking that the logic and the order handling work. It is poor evidence about profitability once targets drop under about 5 pips.
If demo results and a tiny live account diverge, the difference is the execution gap, and it can be measured. Record for every trade the signal price, the fill price and the time between order and fill, then average slippage by hour. That table is worth more than another month of demo equity curve.
Has anyone run the same system on demo and live simultaneously, and what was the per-trade gap?
For a swing trader this barely matters. For a scalper with a 3 pip target, 0.3 pip of extra slippage on both sides is 20 percent of the gross target.
Demo is useful for checking that the logic and the order handling work. It is poor evidence about profitability once targets drop under about 5 pips.
If demo results and a tiny live account diverge, the difference is the execution gap, and it can be measured. Record for every trade the signal price, the fill price and the time between order and fill, then average slippage by hour. That table is worth more than another month of demo equity curve.
Has anyone run the same system on demo and live simultaneously, and what was the per-trade gap?