The company said the outage was resolved Friday night after several hours. The glitch affected registers at 7,400 company-operated stores in the U.S. and 1,000 in Canada, and prompted some stores to give away drinks.
"All Starbucks stores in the U.S. and Canada are expected to open for business as usual on Saturday," the company said in a statement late Friday. "We apologize to our customers for this inconvenience."
Starbucks said the outage was caused by "a failure during a daily system refresh." Jim Olson, a company spokesman, stressed it was an internal issue and that no external breach was involved.
The problem began in the evening Friday on the East Coast, with workers posting hand-written "Cash Only" signs on windows and giving away free drinks and food because they were unable to ring up orders on registers. Starbucks initially said stores would remain open during the outage, then changed course and said it decided to close stores early.
At a Starbucks in Seattle, customers were told workers couldn't process orders and were offered coffee at no charge.
"I'm not going to complain about a free cup of coffee," said Suveer Sharma, who stopped in before heading on a trip to Idaho.
Others at a Starbucks in Phoenix weren't as happy.
"I have a sleeping baby in the back and I'm waiting for a prescription," said Claudia Larson, 40, of Scottsdale. "I wanted a coffee! I'm bummed!"
Starbucks stores are typically busiest in the mornings when people are on their way to work, meaning the impact of the outage on sales could have been far worse. Still, the company has been trying to attract more customers in the late afternoons and evenings with an expanded menu of food and drinks.
Most fast-food and restaurant chains have some type of computer system that lets them track sales at registers companywide, said John Gordon, a restaurant industry analyst and consultant. But Starbucks is different from many others because it owns the majority of its locations in the U.S., whereas chains like McDonald's are mostly owned by franchisees.
That could mean the sales register system Starbucks uses is far more integrated across stores, Gordon said.
In Williamsburg, Virginia, Tom Roberts was part of two couples who stopped by a Starbucks after dinner. He said they accepted the store manager's offer of free coffee or tea.
"They were super polite in coping with it," he said of Starbucks staff.
Some customers took the news harder than others.
"One guy had been driving all day, he was anxious for a nice fancy Starbucks — but she gave him a large coffee and he was cool," Roberts said. "I think he had a little craving going."
The company said the outage also affected four Evolution Fresh stores and six Teavana Tea Bar stores. Those stores were also to reopen Saturday, Starbucks said.
Starbucks said the outage did not affect the more than 4,800 licensed Starbucks stores in the U.S., which are in airports, supermarkets and other places. The company also has more than 300 licensed stores in Canada that were not affected.
Associated Press writer Traci Carl contributed from Phoenix. AP Food Industry Writer Candice Choi contributed to this story from New York.