Universe Scanning
Automatically selecting which symbols the strategy watches — the funnel before any rule runs.
What it means
No system watches the whole market at tick resolution; a scanner narrows thousands of symbols to a tradable few by turnover, day change, or a personal list, and keeps that set fresh as the day develops. Your universe is a hidden parameter of every backtest and every live session.
The subtle risk is survivorship inside the day: a symbol that enters the universe after its move began looks, in later data, like it was always there. Recording when each symbol actually entered keeps live behavior and research honest with each other.
Why traders care
- Universe choice often affects results more than the entry rule itself.
- Scanner criteria are strategy: "most active" and "top gainers" produce different games.
In a TraderWe strategy
if InUniverse == 0 and ProfitPct < 0:
Sell()Related terms
Educational content, not investment advice. Engine details describe how TraderWe computes this value; other platforms may define it differently.