DNC has listed the qualifiers, a total of 20 candidates over 2 debates:
Sen. Michael Bennet of Colorado
Former Vice President Joe Biden
Sen. Cory Booker of New Jersey
South Bend, Indiana Mayor Pete Buttigieg
Former HUD Secretary Julián Castro
New York City Mayor Bill de Blasio
Former Rep. John Delaney of Maryland
Rep. Tulsi Gabbard of Hawaii
Sen. Kirsten Gillibrand of New York
Sen. Kamala Harris of California
Former Gov. John Hickenlooper of Colorado
Gov. Jay Inslee of Washington
Sen. Amy Klobuchar of Minnesota
Former Rep. Beto O'Rourke of Texas
Rep. Tim Ryan of Ohio
Sen. Bernie Sanders of Vermont
Rep. Eric Swalwell of California
Sen. Elizabeth Warren of Massachusetts
Author Marianne Williamson
Entrepreneur Andrew Yang
Bullock, Gravel, Messam & Moulton did not qualify
https://www.nbcnews.com/politics/2020-election/dnc-names-20-candidates-who-will-appear-stage-first-democratic-n1017316