The New York Times' acquisition of popular online word game Wordle has triggered an uproar on social media, with worried fans stating the currently free-to-play game might be put behind a paywall.

Announcing on Monday that it had bought Wordle for an "undisclosed price in the low seven figures," the Times said the game would "initially" remain free for existing and new players.

That wording led some social media users to suggest the media company would soon allow only subscribers access.

"I have never seen Twitter as immediately mad as it is about the NYT Wordle buyout," one user tweeted. "The NYT took one nice and simple thing that a lot of people really liked, a dumb bit of fun in our exhaustingly dark times, and implied that they'll stick it behind a paywall."

After creating Wordle to play with his girlfriend Palak Shah, software engineer Josh Wardle released it to the public in October. Within months it became a global phenomenon, with celebrities such as Trevor Noah joining the bandwagon.

The once-a-day online game gives a player six chances to figure out a five-letter word, using the least number of guesses.

"I would be lying if I said this hasn't been a little overwhelming," Wardle said on a post on Twitter. "After all, I am just one person, and it is important to me that, as Wordle grows, it continues to provide a great experience to everyone."

The Times said it expects the acquisition to broaden its digital content as it tries to reach the goal of 10 million subscribers by 2025.

The newspaper was an early adopter of the paywall when it started digital subscription plans back in 2011. That strategy helped it buck the trend of falling print revenues and build a digital business.

It has also bought into other digital media such as subscription-based audio app Audm and product review website Wirecutter. Last month it agreed to pay $550 million in cash for sports site The Athletic.

As the Times also seeks to grow paid readers outside its core news content, games and puzzles have become a key part of a strategy to keep its audience engaged on its apps and websites.

Its Games unit, which has more than one million subscriptions, started with the Daily Crossword, and later launched games such as Spelling Bee, Tiles, Letter Boxed and Vertex.