Stephen Shankland/CNET

When it comes to concerns over new ad-blocking limits planned for Chrome, Google has budged but so far hasn't moved very far.

The company is responding to criticism of proposed changes to its Chrome web browser that may cripple ad-blocking tools. Though Google revealed it's lifting some limits and plans an exemption for enterprise users, it doesn't look like the search giant has been fundamentally persuaded by critics.

Google revealed the changes in October as part of a broader plan to improve Chrome extensions. In January, developers noticed that part of the plan, called Manifest v3, could hurt ad blockers. Manifest v3 is designed to improve Chrome extensions' performance, privacy and security, but one part of that change limits how extensions will be able to examine aspects of websites. Some developers have said this will torpedo their ad-blocking and privacy extensions.

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In response to criticism from developers, Google's Simeon Vincent said the proposed changes in Manifest V3 aim to give end users more control and briefly noted an exception for enterprise users. The Chrome enterprise version offers administrative control options and is free to use.

"Chrome is deprecating the blocking capabilities of the webRequest API in Manifest V3, not the entire webRequest API (though blocking will still be available to enterprise deployments)," wrote Vincent in a Chromium forum post on May 24.

And in a statement, Google said it "supports the use and development of ad blockers." The company is working with developers to create a "privacy-preserving content filtering system that limits the amount of sensitive browser data shared with third parties." It didn't comment in detail, though.

A Google Chrome leader in effect denied any effort to hobble ad blockers.

"The sole motivation here is correcting major privacy and security deficiencies in the current system. I know, because I set that focus, and the team reports up through me," Chrome security leader Justin Schuh tweeted Thursday.

And Alex Russell, a Google web standards leader, likened the change to the shift Chrome originally made with a more limited extensions foundation compared with the all-purpose framework built into Mozilla's Firefox browser at the time. Mozilla has since moved to a framework called Web Extensions that mirrors Chrome's.

"We all learn the hard way that providing nice things and hoping they don't get misused eventually get users hurt. So this is a correction whose details are being honed," Russell tweeted. Figuring out how to improve performance and security without hampering utility is tough, but, he added, "I can assure you the extensions team hasn't stopped listening."

Ad blocker objections

Content blockers are a major part of the internet, with 615 million devices using them, according to a 2017 study by PageFair, a company that tries to help publishers cope with the technology. Content blockers' most visible effect is often blocking ads, but they also can block tracking software ads use -- even when ads themselves are invisible. Examples include uBlock Origin, AdBlock Plus, Ghostery and Privacy Badger.

One of the most prominent objections came from Raymond Hill, developer of uBlock Origin. He said this week that the new ad-blocking approach "benefits Google's primary business," advertising.

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 advertising-related internet addresses.

The new approach has a proposed limit to those rules -- a maximum of 30,000 -- which would hobble ad blockers and other software using those lists. uBlock Origin employs more than 90,000, Hill said. He didn't immediately respond to a request for comment.

Although Hill raised the point that Google benefits when ads aren't blocked, it's not clear that Google's proposed ad-blocker changes would shelter its ad business in any way. Even a short list of rules could easily include Google's ads, and indeed likely would given Google's power in online advertising.

Google lifting ad-blocker limits

Google added a more flexible mechanism, dynamic rules, in response to concerns from content blocker developers, Vincent said. That's currently got a limit of 5,000 rules. However, Google does plan to raise its limits to some as-yet-unknown number.

"We are planning to raise these values, but we won't have updated numbers until we can run performance tests to find a good upper bound that will work across all supported devices," he said.

The complaints have opened a door to Chrome competitors, though, with some content-blocker fans discussing a move to Mozilla's Firefox, Brave Software's Brave and Microsoft's new Edge that's based on Google's open-source Chromium browser foundation.

Brave, also based on Chromium, has ad and tracker blocking built in and enabled by default and thus will block that content regardless of Google's decisions. But Brave Chief Executive Brendan Eich said Thursday the company will maintain Chrome's older extension interface so uBlock Origin and another blocker from Hill, uMatrix, will continue to work.

"We will support uBO and uMatrix," Eich said.

Firefox, too, looks likely to stay the course. "Firefox continues to allow ad-blocking extensions to work in the browser. We don't have any plans at this point to change that," Mozilla said in a statement.

Google changes to Manifest v3

Google wants to move from an application programming interface (API) called webRequest that blockers use to run their rules and move instead to a new one called declarativeNetRequest. "The big problem with webRequest is unfixable privacy and security holes," Google's Schuh said.

Hill also objects to the new interface's limited flexibility for running its rules, saying declarativeNetRequest's abilities are "set in stone" and not something uBlock Origin can adapt to use.

But another Chrome security team member, Chris Palmer, said the new interface will improve blockers.

"The new extension APIs are not going to break content blockers, but it will help them work more safely and potentially faster," Palmer tweeted.

But it's clear Google hasn't convinced its critics.

Originally published May 30, 8:13 a.m. PT.

Updates, 10:59 a.m.: Includes more about Google's plans and the objections to them; 3:36 p.m.: Adds comment from Mozilla; 3:55 p.m.: Includes comment from Google; May 31, 9:27 a.m. PT: Adds comment from Google's Alex Russell.