"That's up from about one-fifth of spending in 2012 and is set to rise to nearly one-third of the total by the end of our forecast period (2018), when advertisers around the world will invest USD 204.01 billion in digital," research firm eMarketer said in its study.
The firm said digital ad spend will make up just over one-quarter of all paid media spending globally.
The total media ad spending worldwide will grow at a significantly slower pace, hovering around 5 per cent for the next several years, it added.
The US is still the single biggest spender on digital ads and North America the highest-spending region.
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"Nearly two in five digital ad dollars this year will come from advertisers in North America, compared with 28.6 per cent in Asia-Pacific where share is actually dropping slightly," it said.
Western Europe accounts for nearly one-quarter of all digital spending around the world and other regions make up just a small share, it added.
While the US is the highest spender on digital media, it is the UK that sports the highest share of total media spending on digital channels, at 47.5 per cent expected this year.