What Is a Stock Screener, and What Should You Screen For?
The short answer. A stock screener is a filter over a database of companies: you set conditions — market value above $1bn, dividend yield over 3%, debt to equity below 1 — and it returns every company that matches. It is a tool for narrowing thousands of possibilities to a readable list. It is not a tool for deciding anything, and treating its output as a buy list is the most common way people misuse one.
What should you screen for?
Start from a thesis, not from the filters. A screen is only as good as the question behind it, and "show me good stocks" is not a question. Three that are:
| Question | Filters that express it |
|---|---|
| Quality at a fair price | High return on equity, moderate P/E, low debt, positive free cash flow |
| Sustainable income | Yield 3-6%, payout ratio under 70%, dividend not cut in ten years |
| Out of favour but solvent | Price well below its 52-week high, net cash, still profitable |
What are the classic screening mistakes?
- Screening on price alone. "Down 60%" is not a thesis; most things that fall 60% deserved to.
- Using ratios across incompatible industries. A bank's debt-to-equity and a software company's are not the same measurement.
- Forgetting survivorship. A screener only contains companies that still exist.
- Over-filtering. Add enough conditions and you will find three companies, all of them by coincidence.
- Treating output as conclusion. The screen produces a reading list.
What makes one screener different from another?
Coverage and the metrics it holds. Most free screeners cover US listings only and carry only what comes off an exchange feed — price, volume, market value, simple ratios. Coverage of non-US markets, and derived metrics like a fair value estimate or an ownership count, are what change a screen from "companies with a low P/E" into "companies with a low P/E that professional investors are also buying".
Is a free screener good enough?
For most private investors, yes, comfortably. The paid tiers of most services sell depth of history, export, backtesting and alerts. None of those affect whether the underlying idea is sound — that comes from reading the company, which is free.
What this cannot tell you
Whether any company on the list is a good investment. A screen matches conditions; it has not read an annual report, and it cannot see a lawsuit, a departing chief executive or a collapsing end market.
Educational information, not financial advice. Every figure on this page is read from the source filings when the page loads rather than written into the article, so what you are reading is today's data and not a snapshot of the day it was published.
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