Is the data displayed under shortable shares real time?

Yes, data displayed under the Shortable column for shares available for short selling is in real-time and no subscription is required.

The amount displayed in the Shortable column will update in a tool tip pop up each time you hover your mouse over the field.

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Is live data provided for paper trading accounts?
How do I see whether a stock is shortable on TWS?
The order entry window is missing shortable and consolidated information