Integral Ad Science Inc. has acquired ADmantX SpA, a European ad tech firm that gives advertisers more information about the content and context of the articles on which their ads could run.

New York-based IAS’s ad verification services already help advertisers track when ads are actually showing up on people’s screens after they click on a page. Its new purchase could help them cater to marketers who increasingly want to know more about the content that surrounds their ads on-screen.

Rival ad measurement firms have also been investing in companies that promise advertisers more clarity and control over where their ads appear online. Earlier this year, IAS competitor DoubleVerify Inc. purchased Leiki, which also specializes in classifying web content. In September, Nielsen Holdings PLC took a minority stake in OpenSlate, which categorizes videos on YouTube and Facebook Inc. to help advertisers choose content that suits them.

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“It is critically important to ensure the content and context where our clients media may appear is not only brand safe but suitable for their brand,” said David Murnick, executive vice president of digital operations and technology partnerships for Amplifi U.S., a media investment arm of Dentsu Aegis Network.

“That’s why you are seeing more acquisitions of this kind,” he added.

Brands have felt burned by occasional episodes when their ads have inadvertently turned up alongside offensive or violent content. But the increased attention to context also owes partly to government regulations such as the General Data Protection Regulation in Europe and the California Consumer Privacy Act, which are complicating data-driven consumer targeting online. As a result, marketers are showing renewed interest in targeting ads based on certain kinds of content, said Adam Gitlin, president of Annalect, the data and marketing sciences group of Omnicom Media Group.

“There is more interest in developing more refined contextual and content-based targeting products, of which brand safety is just one part of the spectrum,” Mr. Gitlin said.

IAS, which was already offering ADmantX services through a tie-up, declined to reveal the terms of the acquisition but said it will take on the company’s entire staff. ADmantX employs less than 50 people, according to a person familiar with the matter. The ADmantX brand name will disappear.

“The ability to categorize and classify content is something our customers have asked us for,” said Integral Ad Science Chief Executive Officer Lisa Utzschneider.

Based in Italy and led by CEO Giovanni Strocchi, a former Vodafone Group PLC executive, ADmantX says it uses natural language processing and machine learning to classify articles on websites. For example, the company’s tech can tell an automotive advertiser whether a particular article includes words such as “crash.”

But the tech can also identify whether articles are positive or negative in tone, Ms. Utzschneider said. That can help advertisers make more nuanced decisions that go beyond avoiding embarrassing juxtapositions. An article covering the auto manufacturer with the best crash-test ratings could be more appealing than one about the auto maker with the worst record.

“It provides another layer of data and information that helps advertisers be that much smarter about what their ads are adjacent to,” Ms. Utzschneider added.

ADmantX’s clients include media companies such as the Financial Times and Comcast Corp. -owned NBCUniversal and Sky, as well as advertisers such as IKEA and Dentsu Aegis Network. The company tracks websites in 29 languages.

IAS was acquired by private-equity group Vista Equity Partners in 2018. At the time, the company had 600 employees and $140 million in revenue.

Ms. Utzschneider said IAS revenue has grown since then but declined to elaborate.

Including the ADmantX acquisition, the company will employ north of 600 employees, she said.

Write to Sahil Patel at Sahil.Patel@wsj.com

Corrections & Amplifications

The chief executive officer of Integral Ad Science is Lisa Utzschneider. A photo caption in an earlier version of this article misspelled her first name. An earlier version also misspelled the name of the company that Integral Ad Science acquired. It is ADmantX. (Nov. 20, 2019)