Adblock Plus, an ad blocker now used on more than 100 million devices, started out as an almost utopian idea a decade ago. Wladimir Palant, a 20-something developer who was annoyed with intrusive ads online, created it as an open-source project and quickly built it up with the help of volunteers who also wanted to make the internet faster, less cluttered and safer from malware.

Palant wanted publishers to make ads that did not “degrade” internet users with interruption and animation, he wrote on his blog in 2007. As Adblock Plus surged in popularity, he was able to turn it into a full-time job, increasing its staff to three employees in 2011 and housing it under a company named Eyeo GmbH in Germany. Its motto: “We want to make the internet better for everyone. Purging bad ads is a good start.”

But shortly after that, in 2011, Adblock Plus was altered and became a tool that, instead of blocking bad ads, allowed ads it deemed “acceptable” to be seen, often for a price — a controversial move that has positioned it as a gatekeeper between advertisers and its huge user base.

Now, with a staff of about 70, the company has moved even deeper into that business with an automated online advertising service that will allow more websites to place ads deemed “acceptable” in front of Adblock Plus users. It is a coveted group for advertisers and publishers: Users are often relatively young, well-educated, tech-savvy and hard to reach. But the introduction of the service last week ignited a backlash among consumers, who accused Adblock Plus of veering from its purpose.

“It’s just the words we use for it that are confusing people,” Ben Williams, director of communications and operations at Eyeo, said in an interview. “We are called Adblock Plus, and for branding reasons, we are not going to call ourselves something different. But if we could, we would call ourselves something like ‘web customizer,’ because that’s really what we want to do for our users.”

Users of Adblock Plus are a “valuable segment,” he added, that has “said they don’t want intrusive ads and are demanding to be reached in a different way.”

The new platform will essentially allow publishers to choose from ads that Adblock Plus deems acceptable. They can then display these ads on their sites. In explaining the service on its website, Adblock Plus said it would help publishers make money when an Adblock Plus user saw that “preapproved” ad instead of a blocked space, adding that it had “been waiting years for the ad industry to do something consumer-friendly, but also industry-friendly.”

Many consumers reacted with vitriol online. “You either die a hero or you live long enough to see yourself become the villain,” one Reddit user wrote in a thread of nearly 2,000 comments discussing the change. Reviews for Adblock Plus in Google Chrome, which routinely yield five stars, showed a flood of one- and two-star reviews after the announcement.

“Who do you think you are?” one user wrote. “The internet police?”

Adblock Plus has long had a list of criteria for what constitutes an acceptable ad. As per its rules, ads must be clearly identified and placed so they do not “disrupt the user’s natural reading flow,” for example, and they cannot pop up, animate or contain images that enlarge.

For several years, companies have been able to reach Adblock Plus users by creating ads that adhere to these guidelines and by undergoing a vetting process. The Adblock Plus website says it takes about 10 working days for ads to be deemed acceptable, or “whitelisted.” (The company says its new service will make that process almost instantaneous.)

The vetting includes an application, outreach from Eyeo, a signed agreement and a proposal posted to an open community message board. Adblock Plus explained that such efforts, along with monitoring individual ads and providing technical support, require funding beyond donations. Before it began whitelisting ads, Adblock Plus accepted donations and funding to become a company, although it does not disclose its financial details.

Adblock Plus says it charges only large entities, which it defines as those that increase their ad impressions by 10 million or more a month once they have access to Adblock Plus users. And Adblock Plus typically takes a 30 percent cut of the money brought in by those ads that would otherwise not be seen by its user base. One example is ads that say “Sponsored Links by Taboola” that often appear at the bottom of websites. According to the Adblock Plus forums, Taboola, a content-marketing company, has been accepted by Adblock Plus, to the consternation of some users.

Adblock Plus says it ends up charging only 10 percent of its whitelisted publishers, those that reach the impressions threshold, and does not take a cut from the other 90 percent.

Regardless, over the last few years, this toll has infuriated publishers and advertisers who do not want to pay Adblock Plus but are keen to reach its audience. As of June, Adblock Plus accounted for about 60 percent of the 220 million ad blockers installed on desktop browsers, according to PageFair, a startup based in Dublin that develops software to fight ad blockers.

The new ad platform is alarming because it “allows them to do this at scale,” said John Montgomery, executive vice president of brand safety at the advertising giant WPP’s GroupM.

“It scares me,” he said. “It makes me uncomfortable that Adblock Plus would be the arbiters of what is good and what is not good.”

Adblock Plus, which partnered with the advertising-technology company ComboTag to create its new platform, also attracted criticism last week after Adblock Plus announced that, as was reported by The Wall Street Journal, the new venture planned to use ad platforms operated by Google and AppNexus, a major automated online ad tech firm. Both companies, which represent the biggest advertising marketplaces, were swift to deny involvement with Adblock Plus, and both terminated ComboTag’s account with them.

“We have no involvement in their program, and this is not a business we want to be part of,” Google said in a statement. The chief executive of AppNexus, Brian O’Kelley, said in a blog post that it had not and would not allow ComboTag to “use our platform to monetize Eyeo and AdBlocker Plus.”

“We found that surprising, but we didn’t find it in the least disheartening because it’s an open system, and we built this to not be dependent on anyone on the demand side, and we fully expect to continue,” Williams, of Eyeo, said. He added that 1,000 publishers signed up on its webpage to test the beta version of its platform.

“At the end of the day, it’s just that people haven’t quite wrapped their heads around exactly what our value proposition is,” he added.

Google was among the companies and trade groups that last week announced their participation in a new organization called the Coalition for Better Ads. The group said in a statement that it planned to “implement new global standards for online advertising,” acknowledging the rise of ad blocking.