Stephen Shankland/CNET

Google isn't trying to kill ad blockers. That's the message in a pair of Google blog posts published Wednesday in response to criticism of the search giant's plan to improve extensions in its Chrome web browser.

"We are not preventing the development of ad blockers or stopping users from blocking ads," said Devlin Cronin in a post on the Google Security Blog. "Instead, we want to help developers, including content blockers, write extensions in a way that protects users' privacy."

Google in October revealed a broad plan to improve Chrome extensions. In January, developers noticed that part of the plan, called Manifest v3, could hurt ad blockers and other extensions that modify website content. Manifest v3 is designed to improve Chrome extensions' performance, privacy and security, but one part of that change limits how extensions can modify websites according to a long list of rules -- blocking content from internet addresses that supply ads, for example. Some developers have said this will hobble their ad-blocking and privacy extensions.

"There's been a lot of confusion and misconception around both the motivations and implications of this change, including speculation that these changes were designed to prevent or weaken ad blockers," said Google's Simeon Vincent in a post on the Chromium Blog. "This is absolutely not the goal."

Ghostery threatens an antitrust lawsuit

Some extension authors aren't mollified, though.

Ghostery, maker of a tracker-blocking extension, still doesn't like the new, somewhat higher limits and raised the prospect of legal action against Google.

"This would basically mean that Google is destroying ad blocking and privacy protection as we know it," Ghostery President Jeremy Tillman said in a statement. "Whether Google does this to protect their advertising business or simply to force its own rules on everyone else, it would be nothing less than another case of misuse of its market-dominating position. If this comes true, we will consider filing an antitrust complaint."

However, it's not clear how the move would protect Google's ad business. Even with a sharply curtailed list of filters, Google's ads could still be blocked, and given its power in online advertising, it's likely an ad blocker would indeed tackle Google's ads.

Part of the debate concerns rules that ad blockers use to decide what to screen and what to display. Chrome's current design permits lots of those rules, so for example an ad blocker can check to see if elements on a website are coming from a very long list of ad-related internet addresses. The new approach had a proposed limit to those rules, a maximum of 30,000, which could've hobbled ad blockers and other extensions using those lists.

Google didn't respond to a request for comment.

Google lifts extension limits some

On Wednesday, Google said that it's raising the limit to a global maximum of 150,000 rules. Last month, the search giant also said it plans an exemption for enterprise users.

Google stressed in its posts that Manifest v3 is still in development and that it'll work with developers. However, the company feels it's making the "right choice to enable users to limit the sensitive data they share with third parties while giving them the ability to curate their own browsing experience."

John Wilander, a programmer behind the Intelligent Tracking Prevention technology in Apple's Safari, expressed some sympathy for Google's stance. "The privacy and security threats of extensions are real. The perf hit of intercepting all network requests, too," Wilander tweeted. But he also spotlighted the importance of Google's change given that "the browser itself offers no modern privacy protections," he tweeted.

Those who question Google's motives, though, also need to look at who's behind the Chrome extensions changes, said Malte Ubl, technical leader for Google's AMP web publishing technology.

"Given that the literal inventors of usable security are driving these decisions, I typically err on not second-guessing their decisions without an army of studies and data," Ubl tweeted. "Five years ago both Android and iOS still thought all apps should have access to your address book by default. We as an industry have since learned that wasn't a good trade-off...It isn't great to give extensions the power to observe and change all web traffic," he added.

Opportunity for rival browsers

The Chrome change has turned into an opportunity for rival browsers also using Google's open-source Chromium software foundation to try to stand out. Brave, Vivaldi and Opera will keep the old browser extensions interface, the companies told ZDNet.

Microsoft, whose Edge browser is the newest member of Google's Chromium community, said it's still evaluating its options.

"We are in ongoing discussions with a number of popular extension developers and with the Chromium community to understand both the technical merits and the impact to developers and customers of the proposed changes," said Kyle Pflug, Edge project manager, in a Reddit forum post Thursday.

Originally published June 12.

Update, June 12: Adds more details on the planned changes to Chrome extensions. Update, June 13: Adds more background and reactions from Ghostery, Microsoft and others.