Demo servers and weekend quotes

[Shadow Trader]

Demo platforms sometimes continue to show moving prices on Saturday and Sunday, when the real market is closed. It looks like free practice time. It's actually a trap for the unwary.

Weekend demo quotes are often simulated or generated by random walks, not derived from real market data. Patterns found in them have no connection to real price behaviour, and any strategy tested on them is meaningless.

Even on weekdays, demo feeds can differ from live ones. Some demo servers use delayed or simplified quotes, show different spreads, or lack the spikes seen during news. Execution is typically instant and without slippage.

For serious testing, it's best to use demo accounts that mirror the live environment as closely as possible, and to avoid any data from periods when the real market is closed.

A related issue appears in historical data. Some data sources include weekend bars filled with flat or synthetic prices. Cleaning them out avoids distorting indicators and statistics.

Another point is the historical data stored on the demo server. Some demo accounts have shorter or lower-quality history than live ones, so backtests and indicators calculated on demo may differ from those on a live account at the same broker.

Using the live server's data, even while trading on demo, is often possible by logging in to a live account in read-only mode, and gives results closer to reality.

Has weekend demo data ever been used in testing, and how was it discovered to be unreliable?