The search giant is the UK’s largest player, generating £4.43 billion of ad revenues in 2017, a figure predicted to rise to £5.1 billion by 2019.
Facebook, which has been on the receiving end of criticism over its audience figures, is expected to hit the £1.87 billion revenue mark this year, thanks to the success of Instagram and continuing investment in video. It is expected to attain an 18.3% share of the digital ad market by 2019, generating £2.57 billion in revenues.
Overall digital ad spend will reach £10.89 billion by the end of 2017, eMarketer said, up 11% on 2016. This growth is accounted for by mobile’s increasing dominance, which will see 30.3% growth this year, while within mobile, video has seen the most growth, at 47.7%. Unlike the digital market, traditional media adspend remains relatively flat.
Traditional media has ailed as digital has thrived. According to eMarketer, TV ad expenditure, which accounts for 21.1% of overall media spend, will fall 2% in 2017 compared with last year. The most pronounced decline among traditional media was for newspapers, down 9% in 2017 compared with 2016, while magazine spend fell 4.5%.
Elsewhere, there was some traditional media growth, albeit marginal. Out-of-home grew 1.4% and radio expenditure was up just 0.3%.
Bill Fisher, senior analyst at eMarketer, said: "There have been signs of tough times ahead for the UK ad industry.
"Despite uncertainty around Brexit and struggles among some of the big agencies, digital continues to attract ad spending, with Google and Facebook the biggest beneficiaries.
"That they’re attracting such spend is perhaps a symptom of the wider market concerns, with brands looking to get the biggest reach for their buck - something that Google and Facebook clearly offer."