Screeners and Scanners

Screeners and scanners covers tools used to filter securities by selected criteria or monitor frequently refreshed market data for trading conditions.

Use this branch when the question is about how a tool selects, filters, ranks, or alerts on securities. The canonical article treats screener and scanner as two timing modes in one discovery workflow rather than as independent investment conclusions.

What This Branch Covers

Decision Lens

Screeners and scanners are discovery tools. Their output depends on the universe, filters, data refresh, missing-data treatment, and vendor definitions; results need independent verification before being used as research, trading, or valuation evidence.

Move to Market Data, Tickers, and Tapes when the issue is the underlying data. Move to Listings and Securities when the issue is whether a security is listed, restricted, or correctly identified.

Evaluation Checklist

• Identify the screen universe, criteria, data vendor, update frequency, effective dates, and result timestamp.
• Check whether the tool uses live, delayed, adjusted, or derived data.
• Confirm ticker, exchange, security identifier, and liquidity before relying on a result.
• Review how missing values, duplicate listings, suspended securities, and corporate actions are handled.
• Treat results as leads for research, not final evidence.

Common Mistakes

• Treating a screen as a recommendation.
• Comparing screeners with different universes or data vendors.
• Ignoring stale or delayed scanner data.
• Overlooking low liquidity after a stock passes a filter.
• Forgetting that filter definitions can differ across tools.

For broader context, return to Market Data, Tickers, and Screening Tools.

In this section

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