Facebook plans to start opening Bay Area offices in May on a rolling basis depending on local COVID data, the company said Friday.

“The health and safety of our employees and neighbors in the community is our top priority and we’re taking a measured approach to reopening offices,” Facebook spokeswoman Chloe Meyere said. “As we return to the office, we have a number of safety protocols in place including physical distancing and masks required at all times when in an office, and where possible, weekly testing requirements for anyone working on site.”

Three Bay Area counties — Santa Clara, Marin and San Francisco — this week moved into California’s less-restrictive orange coronavirus tier, which allows offices to re-open with modifications. San Mateo County moved into the orange tier last week.

Uber said Friday it would start opening its new headquarters building in San Francisco’s Mission Bay neighborhood on Monday.

Facebook will start the Bay Area re-opening May 10 at its Menlo Park headquarters, Meyere said. The Fremont office will follow May 17, the Sunnyvale office May 24 and its offices in two downtown San Francisco towers on June 7, she said. Offices will initially be opened with a maximum seated capacity of 10%, on an opt-in basis for employees now working remotely, she said.

“This is a desk in a physically distanced room with safety protocols,” Meyere said.

In announcing the return-to-offices plan, the Menlo Park social media giant cited increased availability of COVID vaccines, but cautioned that the re-openings depend on health data showing continued improvement.

Facebook had given employees world-wide until July 2 to continue working from home, and is now moving to a site-by-site approach, it said. The company said data indicates that the earliest it could open large offices such as the Menlo Park headquarters at 50% capacity would be after the first week of September.

Facebook expects that once conditions allow an office to reach 50% capacity, employees assigned to that office and still working remotely will be asked to return a month later, Meyere said.

The company plans to start re-opening its Seattle offices next month, also at 10% capacity, Meyere said.

Decisions about bringing workers back into offices will be based on data including local COVID rates, vaccination rates, access to testing and treatment, government guidance, and health data from sources such as the U.S. Centers for Disease Control and World Health Organization, as well as Stanford Health.

Facebook workers won’t have to be vaccinated to return to the office, but the company is encouraging its employees to get the vaccine, Meyere said.

Employee perks including free food and shuttle buses will remain on hold indefinitely, although transit stipends will be available for workers going back to offices, Meyere said.

Facebook CEO Mark Zuckerberg said last year that he expects up to half the firm’s workforce may be remote within five to 10 years. However, Meyere said, “We’re still committed to our offices.”

The San Francisco Chronicle first reported Facebook’s new re-opening plan.

Uber, which had earlier extended its work-from-home policy until Sept. 13, said it would open its new headquarters at 20% capacity on Monday, on a voluntary basis. “As one of the world’s largest platforms for local transportation, we know Uber has a critically important role to play in bringing cities back to life,” the ride-hailing giant said in an emailed statement, adding that its COVID-safety protocols meet or exceed global, national and local guidelines. Masks will be required in the office, and desks will be at least six feet apart, the firm said.