A report has found that the use of ad blockers has grown 41 percent in the past year and estimates it will cost the industry $21.8 billion globally in lost advertising revenue in 2015. It goes on to warn that the software now poses a significant threat to the future of free content on the web.

The cost of ad blocking’ study from PageFair and Adobe said that almost 200 million monthly internet users are now deploying browser extensions that block ads. It went on to say that sites targeted at "young, technically savvy, or more male audiences" are the most affected by ad blockers.

The rate of ad blocking varies country by country. The US has an estimated 45 million monthly active ad block users - still some way behind Europe's 77 million users. Greece has the highest rate of ad block usage in Europe, with 36.7% of internet users in the country utilizing the software.

Sean Blanchfield, the co-founder and chief executive at PageFair, said: "It is tragic that ad block users are inadvertently inflicting multi-billion dollar losses on the very websites they most enjoy. With ad blocking going mobile, there’s an eminent threat that the business model that has supported the open web for two decades is going to collapse."

The report explains that the use of ad blockers, which are still primarily found on desktop and laptop browsers, has started to spread to mobile devices in Asia. The trend is likely to increase worldwide in September, as Apple plans to introduce ad blocking support to the Safari mobile browser for iOS 9.

PageFair, which provides counter ad block solutions to web publishers, has been tracking the growth of ad blocking for three years. The company provides publishers with analytics to measure how many of their visitors are blocking ads, and works with the makers of ad block plugins in order to display ‘non-intrusive’ ads to those who use ad blocking software.

Industry giant Adobe is backing PageFair’s attempts to circumvent ad blocking browser extensions. “By working with PageFair, our goal with this research is to shed light on the effects of ad blocking so the industry can develop better solutions for content publishers, advertisers and consumers alike,” said Campbell Foster, a director of product marketing at Adobe.

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