According to ad verification firm Meetrics, the viewability of ads served in the UK reached its highest level in the first quarter since Q3 2014, when 55% of ads were viewable.
For the report, an ad was considered viewable if it met the recommendation set out by the Internet Advertising Bureau (IAB) and the Media Rating Council that 50% of it can be seen for at least one second.
However, while advertisers should be heartened by the improvement, the data showed that the UK continues to lag behind other European markets.
For example, two-thirds (66%) of ads served in France were judged to be viewable over the same period, with similar levels in Austria (65%) and Germany (60%).
Anant Joshi, director of international business at Meetrics, said there were two main reasons to explain the improvement in the UK's ad viewability rates.
"As the whole 'ad verification' topic gets more publicity, it gains prominence in marketing departments. Consequently, more campaigns are being optimised against viewability figures," he said.
"Furthermore, the issue of low-viewable inventory in programmatic – which now accounts for 60% of display ad sales – is being addressed."
The report also examined the main reasons why some ads are not seen. Based on 100 measured ads in one campaign, Meetrics found that 15.1% of ads were not viewable because the ad did not load fast enough before the viewer had moved on.
Another area of concern was that 12.8% of ads appeared before the fold, or below the part of the page in view.
"A key route to improving viewability is increasing web-page performance and ad serving systems, notably drastically reducing the amount of web browser redirects going on behind the scenes before content is loaded," Joshi said.
"Initiatives like the IAB's Lean Ad Principles – actually designed to counter ad blocking – should have a positive knock-on effect on viewability," he added.
Data sourced from Meetrics; additional content by Warc staff