Most employers spend less than an hour in preparation ahead of interviewing job candidates, but usually make checks on their social media, research has found.
A study by jobs site totaljobs showed that only a third of candidates expected their social media to be screened.
One in three people going for a job spend over three hours preparing for an interview, the survey of 8,500 candidates and 260 recruiters discovered.
Matthew Harradine, director of totaljobs said: "When it comes to interview preparation, our research reveals a wide discrepancy between candidates' expectations and employers' behaviour.
"Whilst the time spent preparing for an interview is much less for employers than candidates, the anticipated methods of researching online and particularly on social media, are widely underestimated by those being interviewed.
"Interviewers use social media to better understand the person they're interviewing.
"Candidates need to make sure that they're aware of their privacy settings and the effect that public posts can have on whether or not they get the job."