Facebook was hit by technical problems yesterday that resulted in extremely slow or no service to some of its 500m users, including those in the UK.
Engineers at the firm described the two-and-a-half hour outage as the worst in over four years.
But the social networking site says the technical difficulties have been resolved, according to US reports.
The problem also appeared to affect the Facebook feature integrated into other websites which allows visitors to "like" articles or videos.
Facebook has not confirmed what caused the service failures, saying only that the company was experiencing "some site issues causing Facebook to be slow or unavailable to some users."
The company later said, without offering any details, the issue had been resolved, but some media reports cited Facebook engineers who blamed a failure in handling an error condition.