What data is used on last candle?

The final candle on the stock chart (today's date) uses real-time data. This data is updated every 5-10 seconds.

Depending on your selected chart time frame, you may not see this candle move.

To test whether the real-time data is updated, you can navigate to the 1 day (1D) time frame and you will see a new candle every 60 seconds during trading hours.