Back in 2015, Google wooed disgruntled publishers with a digital tool called Accelerated Mobile Pages, or AMP, to boost traffic to their mobile websites.

That charm offensive is now backfiring.

European and American tech, media and publishing companies, including some that originally embraced AMP, are complaining that the Google-backed technology, which loads article pages in the blink of an eye on smartphones, is cementing the search giant's dominance on the mobile web.

That growing criticism could give the California company another antitrust headache in Brussels — just when it is on deck for a possible multibillion-euro antitrust fine from the European Commission related to Android, its popular mobile software. Google denies any wrongdoing in that case.

With AMP, Google uses its global scale and virtual monopoly in search to woo people into its digital universe and create a de facto on-ramp for vast swathes of internet traffic, according to more than a dozen EU and U.S. publishers, web developers and open-source software companies. Most spoke to POLITICO on the condition of anonymity because they were not authorized to speak publicly about their relationship with Google.

“We are moving from a world where you can put anything on your website to one where you can’t because Google says so” — Joshua Benton, Nieman Journalism Lab

Some say that Google penalizes publishers that do not use AMP by ranking their links lower than others in search results, an accusation the tech company denies. For others increasingly reliant on the digital tool, there's a growing frustration that Google imposes tough restrictions on the type of online advertising displayed on mobile pages via AMP, curbing much-needed revenue for websites.

“There is a sense in which AMP is a Google-built version of the web,” Joshua Benton, director of the Nieman Journalism Lab at Harvard University. “We are moving from a world where you can put anything on your website to one where you can’t because Google says so.”

Already confronted with a series of antitrust charges, Google, according to its corporate rivals, is doubling down on its online dominance with technologies like AMP that, in their view, crowd competitors out of the mobile internet. The technology already provides, on average, roughly one-fifth of mobile traffic to sites that use it, according to ChartBeat, a data provider.

“People aren’t served well when one entity has a stronghold on users’ data or dominance on a particular platform,” said Denelle Dixon, chief operating officer of Mozilla Corporation, a competitor to Google in some online services. That approach, she continued, risks affecting “competitive dynamics” online.

Google competition troubles

Google's rivals frequently grumble to investigators in Brussels and national capitals about AMP, which is open source, but mostly controlled by the tech company. In response to these informal complaints, competition authorities have not signaled whether there are grounds to open yet another front in Europe's already intense, and lengthy, antitrust standoff with the search giant. A spokesman for the Commission declined to comment.

Google denies that AMP gives it too much sway over the mobile web. As it is viewed as a so-called dominant company under EU competition rules, following a previous Commission's antitrust ruling against the company last year, the search giant must now tread carefully when expanding its digital empire for fear of sanctions.

"Thousands of publishers around the world use AMP to create websites and ads that are consistently fast across devices and platforms, while remaining in full control of their pages and data," Google said in a statement.

The focus on AMP, particularly as people's internet habits shift to their smartphones, comes at a difficult time for Google and its mobile strategy.

Margrethe Vestager, Europe's competition chief, is mulling a possible multibillion-euro fine against Android that could come as early as the summer, according to several people familiar with the case, who spoke on the condition of anonymity. And the search giant already is appealing a European Commission antitrust ruling — and €2.4 billion fine — in 2017 that it abused its dominant position in online search.

With the Commission in the final stages of its Android case, competition experts and politicians warn that Vestager’s focus on the mobile software is fast becoming yesterday's news amid Google’s rollout of other mobile technologies, including a smartphone-based travel booking service and so-called ad blocking on its Chrome mobile browser.

“AMP is an example of Google dialing up its anti-competitive practices under the nose of the competition regulators,” said Ramon Tremosa, a Spanish member of the European Parliament, who is a vocal critic of the search giant.

Vestager has not addressed AMP directly. But in March, she warned powerful players like Google about extending their reach elsewhere. “Companies that dominate their markets have a special responsibility to make sure that their actions don't harm competition,” she told an audience of German competition lawyers.

Outreach to old media

When Google first released AMP, its aim was twofold: to woo publishers and ward off Facebook, its main competitor.

Media companies, mainly in Europe, had spent years lobbying local lawmakers that Google unfairly drove traffic away from their sites. In response, the search giant teamed up with many of these publishers to develop AMP in the hopes of winning over skeptics whose close ties to politicians could harm its online empire.

The technology allows publishers’ mobile sites to be stored in Google’s own servers and preloaded on individuals’ smartphones, significantly reducing lag time when people are surfing the mobile web on patchy cellphone networks.

“Publishers are shifting their allegiances toward Google” — John Saroff, ChartBeat

Google says that it does not charge publishers for using AMP, adding that readers benefit from mobile web pages' faster loading times and companies profit from increased advertising because more people visit their websites through the technology.

In roughly four years, AMP now powers over 4 billion web pages on more than 31 million sites worldwide, according to Google's statistics. (POLITICO also uses the technology. The co-owner of its Europe edition, Axel Springer, is a staunch critic of Google’s practices.)

The Google-backed technology also helped the company in its global battle with Facebook.

The social network's rival service had threatened Google’s dominant position in search as people shifted their time online to smartphone apps like WhatsApp and Instagram, digital services owned by Facebook. Its rival Instant Articles product offered publishers an alternative to load mobile stories quickly — and sell more ads.

Yet in the last 12 months, after Facebook announced it would downplay the prominence of articles in people's news feeds, many media organizations pulled back from the social network to focus on Google’s digital tool. That allowed the search company to reinforce its position as a key driver for mobile traffic for sites worldwide, according to industry watchers.

“Publishers are shifting their allegiances toward Google,” said John Saroff, chief executive of ChartBeat, who added that roughly 20 percent of publishers’ mobile internet traffic now originates from Google's AMP compared to 12 percent from Facebook's Instant Articles.

Google’s mobile web

Google has worked hard to reinforce this position on the mobile web.

After initially targeting news organizations, Google began to roll out AMP to the wider mobile internet, allowing e-commerce players like eBay and social media companies like Twitter to similarly speed up, and drive traffic to, their mobile websites.

That prompted hundreds of coders, internet activists and publishers earlier this year to sign an open letter to Google, raising hackles that the mobile technology had increased the company's online dominance. For the more than 600 signees, Google unfairly gave preferential treatment in search to AMP content and stored others' web pages within the Google universe — a practice that included replacing publishers' own links with Google.com domain addresses.

"They say it makes the web faster, but all it does is lures developers into Google's web," said Hans de Zwart, director at Bits of Freedom, a Dutch internet advocacy group, who signed the letter.

In response, Google said it would allow publishers by the end of 2018 to retain their own mobile web links, even if they used AMP, instead of replacing them with Google.com addresses. Sites would also be free to store their pages outside of the company's servers while still benefiting from AMP's improvements.

Some publishers and developers disagree that AMP does not affect their position in online search.

Many are still not convinced by Google’s efforts to open up AMP.

More than half a dozen prominent European and U.S. news organizations told POLITICO that as AMP guaranteed them pole position in Google's search results — the company ranks faster-loading pages higher in its algorithms — they felt an obligation to use the technology. In particular, media sites were eager to be included in so-called news carousels, or exclusive placement by Google at the top of the people’s mobile search results, that often take up a third of people’s smartphone screens.

Google denies it prioritizes AMP content in its online search service, and says that content in its news carousels is not included in determining people’s search results. The company does not specify how it chooses which stories are placed in its news carousel.

Some publishers and developers disagree that AMP does not affect their position in online search. Such prominent placement, according to industry executives, can have a significant impact on media companies’ web traffic and overall advertising revenue.

"If the carousel appears above search results, it's preferential treatment," said Jeremy Keith, founder of Clearleft, a digital design agency that has built websites for several high-profile publishers like Penguin, Pearson and Britain's Channel 4 News.

Over the last year, AMP publishers, for instance, saw their mobile internet traffic roughly double compared to almost zero growth for those who did not use the technology, according to ChartBeat statistics. That increase, analysts caution, may not be solely related to Google's technology, but also can come from websites' own mobile-friendly tactics.

But when a British news outlet began using the AMP technology, according to Barry Adams, founder of Polemic Digital, a marketing media consultancy that helped several publishers develop their mobile websites, the site received more than three times the mobile traffic and was ranked higher in Google's overall search results. Adams declined to identify the U.K. media organization because of a confidentiality agreement with the publisher.

“I see it across all my publishing clients,” said Adams. "Publishers are held hostage by Google."

AMP: who benefits?

Critics are quick to highlight ways in which the technology promotes Google’s interests.

AMP offers the tech company with a readymade format to entice others looking to boost their mobile traffic. But it also consolidates Google's position as an unavoidable and dominant partner for publishers just as people's internet habits turn to smartphones, according to the company's critics and some of its publishing partners.

That reduces incentives for websites, particularly those of smaller companies with limited financial resources, to invest in alternative technologies not dependent on Google's corporate largesse.

AMP leads to "less investment by publishers in formats and distribution," said Angela Mills Wade, executive director of the European Publishers Council, which represents two dozen major press publishers across Europe, including Axel Springer and NewsCorp’s NewsUK.

Other publishers gripe that AMP gives Google access to coveted user data because almost all of AMP traffic currently runs through the company's own servers. That includes information on people's geographical location, how much they scroll up and down publishers' websites and whether they interact with sites' digital advertising.

A Google spokesman said its AMP data collection practices comply with the company's privacy policy.

Nicholas Hirst contributed reporting.