Meta, which owns Facebook, Instagram and WhatsApp, has announced that it will cut 13% of its workforce.
The first mass lay-offs in the firm's history will result in 11,000 employees, from a worldwide headcount of 87,000, losing their jobs.
Meta chief executive Mark Zuckerberg said the cuts were "the most difficult changes we've made in Meta's history".
The news follows major lay-offs at Twitter, which cut about half its staff, and other tech firms.
"I know this is tough for everyone, and I'm especially sorry to those impacted," he wrote in a statement.
Mr Zuckerberg blamed massive long-term expectations for growth based on the firm's rise in revenue during the pandemic.
"Many people predicted this would be a permanent acceleration," he wrote, "I did too, so I made the decision to significantly increase our investments."
Instead he said "macroeconomic downturn" and "increased competition" caused revenue to be much lower than expected
"I got this wrong, and I take responsibility for that," he said.
The announcement of job cuts was widely expected.
Mr Zuckerberg told hundreds of Meta executives of the plans on Tuesday, the Wall Street Journal reported.
Mr Zuckerberg said the company would focus on high-priority growth areas, like artificial intelligence, advertising, and "our long-term vision for the metaverse".
Meta will also cut costs elsewhere - including reducing its spending on buildings and offices, and increasing desk-sharing.
Affected Meta employees will receive an email soon, he said, and will have an opportunity to ask questions.
US employees will receive redundancy payments worth 16 weeks pay plus a week for every year worked. Additional benefits will also include continuing to provide family health insurance for six months.
Support outside the US will be similar, but there will be a separate redundancy process to take into account local employment laws.