Twitter Inc. on Thursday said it would slash 9% of its workforce and redirect its focus from driving growth to delivering profits, an about-face following the retreat of several potential acquirer including Salesforce.com Inc.

The cost-cutting moves, which include shutting down its Vine video app, come as Twitter reported dwindling revenue growth for the third quarter and another loss over $100 million. Revenue rose just 8.2%, compared with over 50% growth in the year-ago quarter.

The...