Two scanners can look at the same stock and report different volume, different prices, and a different ranking — because they're reading different data feeds. For a scanner whose whole job is finding what's moving, the feed isn't a detail. It's the foundation.
What the SIP is
The SIP (Securities Information Processor) is the consolidated tape — it aggregates trades and quotes from all US exchanges into one feed. It represents effectively 100% of US equity trading volume. It's the data professional desks rely on for an accurate, complete picture.
What IEX is
IEX is a single exchange. Its data feed is free or cheap, which is why many budget tools use it — but IEX typically handles only a low-single-digit percentage of total US volume. Scanning on IEX-only data means you're seeing a small, unrepresentative slice of what actually traded.
Why it changes your results
- Volume undercount: a stock's real relative-volume (RVOL) — the #1 momentum tell — can be massively understated on a partial feed.
- Missed movers: low-float names that trade mostly off-IEX can simply not show up.
- Wrong prices/levels: VWAP, highs/lows and gaps computed on partial data are off.
The bottom line
TradeScaner runs on the full SIP feed via real-time WebSocket, so relative volume, prices and rankings reflect the entire market — not a sliver of it. If you're comparing scanners, ask which feed they use. It's the difference between scanning the market and scanning a corner of it.