Jerry, Below is sample of what I can find on ES. I don't know if Pre-market, after-market and real time data are available separately for free.
ESZ18
Time Open High Low Last Change Volume Open Int
10/17/18 2,816.25 2,824.25 2,806.00 2,806.00 -11.75 197,016 0
10/16/18 2,747.50 2,819.00 2,745.50 2,817.75 +68.75 1,780,311 2,739,270
10/15/18 2,770.00 2,778.75 2,745.25 2,749.00 -19.50 1,763,922 2,765,969