The forecast from market research company eMarketer shows that Google is likely to make $72.69 billion in ad revenues in 2017, while Facebook will make $33.76 billion. Together, that equates to a 46.4 percent share of advertisers' total global digital ad spend.
Shelleen Shum, a senior forecasting analyst at eMarketer, credited mobile and video for their dominance.
"This year, Facebook and Google will once again emerge as the global leaders in digital advertising, scooping up almost half of worldwide digital ad money, tapping on continued strength in mobile and video advertising," she said in an emailed statement.
"Facebook and Google's dominance in mobile advertising remains intact as they take up over half of worldwide mobile ad revenues throughout the forecast period.
Advertisers' spend on digital formats globally will increase by 17.4 percent to $583.91 billion, equivalent to 38.3 percent of their entire ad budgets, the report also stated.
Snapchat is set to make more money from advertising this year, growing its revenues to $900 million, representing a hike of 163.3 percent, eMarketer forecasts.
Chinese companies Alibaba, Baidu and Tencent will collectively make $35.82 billion from advertising this year, while Tencent's brand value has topped $100 billion, according to WPP's BrandZ report out this week.
"In the immediate future, the only other potential rivals to Facebook and Google are the big 3 Chinese companies, Baidu, Alibaba and Tencent (BAT), who are riding on a wave of rising disposable incomes and a growing tech savvy population in China. The BAT companies are expected to experience resilient digital and mobile ad revenue growth as they start to fully monetize their various advertising products," Shum added.