Both the Advanced and Mosaic versions of the Market Scanner tool are free to use. However, if you want to see real-time scanner data you must subscribe to market data.
Additional Information
Is the market scanner free to use?
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How do I set up an Advanced Market Scanner?
How can I get a real time chart in TWS?
How do I create a Mosaic Market Scanner?
Do I get real-time P&L without a market data subscription?