Starbucks closed more than 8,000 stores on Tuesday to train around 175,000 employees against racial bias.
The move follows the April 12 arrest of two black men in a Philadelphia Starbucks, which sparked outrage, protests and soul-searching about racial tensions that have deteriorated under President Donald Trump.
For many, the training was overshadowed by ABC's decision to cancel hit sitcom "Roseanne" after its star Roseanne Barr, a Trump supporter, made a remark decried as racist against former White House aide Valerie Jarrett.
"We realize that four hours of training is not going to solve racial inequity in America or anyone coming into our stores who may have a problem," Starbucks executive chairman Howard Schultz admitted on CNN.
"But we have to start the conversation."
While store managers declined to talk to media and the press was not invited to the training sessions, staff were to watch taped messages from Schultz and CEO Kevin Johnson, as well as a message from Common, the rapper and activist.
Employees will watch a film from documentary maker Stanley Nelson on African American history and the civil rights struggle, before discussing in groups their own experience of racial discrimination.
The curriculum, to be made available at a later date, was drawn up in consultation with US president Barack Obama's former attorney general Eric Holder and civil rights lawyer Bryan Stevenson, among others.
As a result, frappuccino lovers had to shop elsewhere. The coffee giant said it was designed to make Starbucks "a place where all people feel welcome."
The company pledged to integrate further trainings in the United States and around the world. Starbucks has 25,000 coffee shops in 70 countries.
Estimated to cost Starbucks $12-14 million in lost sales, the exercise was criticized by some as virtue signaling, but has been cautiously welcomed by black officials and activists.
Sherrilyn Ifill, president of the NAACP Legal Defense and Educational Fund and one of those consulted on the curriculum, said it "created an important window" for retail corporations "to honestly and forthrightly tackle racial inequality."
In New York and Washington, Starbucks customers who dashed out for a sandwich or a caffeine fix before it was too late welcomed the move.
"Smart idea. It should have been done a while ago," sales rep Chad Mittleman, 31, told AFP in Midtown Manhattan.
"At the end of the day, it is all in the attitude and belief of the individual employee," he said. "It's good but I don't know whether it will bring definitive change."
Starbucks announced the training on April 17 as it battled to contain outrage over the arrest of Rashon Nelson and Donte Robinson, apologizing and adopting an open bathroom policy to non-paying customers.
After Nelson and Robinson stepped into the cafe, one of them asked to use the restroom while waiting for a third person to arrive for a business meeting.
Staff refused, on the grounds that he was not a customer. After the pair sat down to wait, the manager called the police.
A video that went viral showed uniformed officers questioning then handcuffing the two men, who put up no resistance, while a white client repeatedly asks an officer, "What'd they do? What'd they do?"
But US social networks have been rocked by a slew of other recent examples of racial discrimination going viral. A student called the police in May when a black graduate student at Yale University fell asleep in a common room.
Earlier this month, a 22-year-old black man was choked by police at a Waffle House in North Carolina after taking his sister to prom, the fourth incident at outlets of the restaurant to attract national attention in less than two weeks.
Other large companies have also adopted racial bias training, albeit with less fanfare. Target introduced its first unconscious bias sessions in 2017, which it says are being rolled out across the company.
American Airlines announced last year that it would train 120,000 employees after the civil rights group NAACP warned against "a pattern of disturbing incidents" reported by African-American passengers specific to the company.