A stock screener is an online tool used by investors and traders to filter stocks based on metrics they put in based on a profile or set of criteria. Screening for stocks enables you to find securities in which you may want to invest. Screeners are an important part of research for serious investors and traders.Some of the data points you can screen for include price, market capitalization, P/E ratio, dividend yield or 52-week price change percentage. Others include average volume and average five-year return on investment (ROI).Related: TWO TYPES OF STOCK ANALYSISLooking For PotentialMost investors use stock screeners to find stocks they believe are undervalued but ready to perform over a certain period. Traders use them to find and identify stocks with potential for short-term action.When using a screener, the more filters you apply, the fewer stocks you will see. Whether using a screener for investing or trading, the main advantage is that of being able to weed out stocks that don’t meet your criteria and present those that do.Using A Stock ScreenerSince a screener is supposed to help you find stocks that appeal to you, to use one, you must ask yourself some questions. For example, are you looking for large cap, mid cap or small cap stocks? Are you interested in companies with stock prices at all-time highs or those that have fallen in price recently?When you finish putting in your criteria, you should get a list of stocks that meet that criteria. It’s important to know that stock screeners are not magic. You can’t, for example, search “companies that make the best products.” You can search for factors that affect a stock’s price such as market cap, revenue, volatility and profit margins. And, of course, you can search on P/E ratio or debt-to-equity ratio.CaveatsIn addition to not being able to search for “companies that make the best products” screeners do not generally provide information about lawsuits; labor disputes or even how happy customers are with the company.Another thing to watch out for is how often the data are updated. Infrequent data updates can feed you old information that is no longer relevant. All-in-all stock screeners are part of a research process that should include many factors.Related: WHEN TO BUY, SELL OR HOLDA Screening WidgetThe FinanceBoards Stock Screener Widget gives you access to more than 400 stock screener performance metrics as they compare to the S&P 500. These metrics can be applied to more than 4,000 publicly traded companies.By adding the Stock Screener Widget to any of your FinanceBoards Research Dashboards, you gain the ability to use those 400 screeners to find new investment opportunities.