First they charge from the company for posting jobs on the their portal, which you can also say as baseline income.
But sometimes they also charge from the applicant to show their profile to top companies to easily get shortlisted. Although the selection is completely depend upon how to you pass the interview.
Some work on commissions that are usually charged to the companies.,
Others as StevenBrown suggested charge the the applicant.
Some job sites function as ATS to help companies manage the hiring process, like a software service.
As others have said, Job sites make money by charging a fee from the companies for advertising their jobs.
Moreover, job sites also charge employers and job boards on a pay-per-click (PPC) basis to promote their
jobs. Similarly, they generate revenue via AdSense, resume search, and strategic relationships.
