Demo and live accounts run on different machines, and sometimes different rules

[Shadow Trader]

A strategy that works beautifully on a demo account and falls apart on a live account is one of the oldest stories in trading. Part of it is psychology. Part is infrastructure.

Demo servers often run on separate hardware, with simulated execution. Fills occur at the displayed price, instantly. Slippage and rejections are minimal or absent. Spreads may be stable, with no widening at news. Volume is unlimited.

Live accounts face real liquidity. Orders travel through risk checks and liquidity providers. Prices change between click and fill. Rejections occur.

Even the price feed can differ. Some brokers use a delayed or smoothed feed on demo. Others use the same feed, but the demo orders are not sent anywhere, so the effect of orders on price is absent.

The only way to know the difference is to run both side by side with the same strategy and compare. A micro account with real money takes the guesswork out.

The effect is largest for scalpers, because the margin between profit and loss is so thin that a half-pip of slippage changes everything.

Another difference is order execution timing. On demo, an order may fill instantly because it never leaves the platform. On live, a round trip through several systems takes tens or hundreds of milliseconds. For a strategy whose entry window is a second long, the gap can erase the edge.

Spread behavior is also different. A demo may show a smooth, narrow spread because it uses a simplified feed. The live spread has bursts, jumps, and gaps that a demo hides.

There is one more factor: the user. Trading with play money changes behavior. Stops are moved more freely, size is larger, and discipline is looser. The numbers from a demo are the product of a different person.

A compromise is to move to live with an account sized for minimal pain, then compare the first hundred live trades against the same period on demo. The difference between the two is a direct measure of how much the demo overstated the strategy.

How big was the gap between demo and live results the first time a strategy went live?