Long lines of limousines stretching out at the V.I.P. entrance. A-list celebrities in luxury boxes flashing on the giant video screens to fans who pay $4,000 for a fifth-row seat and sip $23 Honey Deuce cocktails. It’s the United States Open, one of the glitziest, most expensive and most popular sporting events on the calendar, and it begins on Monday.

For many people the cost is prohibitive.

But there is a way to see great, professional tennis up close for free at the U.S. Open, and it has already begun. In the week before the main draw, several days of high-level, competitive professional tennis are on display on the grounds of the Billie Jean King National Tennis Center in Flushing, Queens, all for free. Anyone can walk in without a ticket.

This pre-tournament tournament, where players battle to qualify for the last 16 spots in the Open, has been free to spectators at least since the tournament moved to Flushing Meadows in 1978. But the event has grown steadily since 2017, when “Fan Week” was officially introduced, with music, children’s events and clinics, and all the food concessions were opened for the first time during qualification rounds.

“I’ve been coming for 15 years and it’s bigger than ever,” said Lissette Molina-Gurevich, an architect from Maspeth, Queens. “I think it’s actually worth paying for, but don’t tell anyone I said that.”