(Adds comments from Facebook, Giphy and antitrust advocacy group)
By Katie Paul and Elizabeth Culliford
May 15 (Reuters) - Facebook Inc is acquiring Giphy, a popular website for making and sharing animated images, or GIFs, and will integrate it with its rapidly growing Instagram photo-sharing app, Facebook said in a blog post on Friday.
The cost, which Facebook and Giphy declined to disclose, was placed at around $400 million by news website Axios.
The announcement comes at a time when the largest social media network is under scrutiny from regulators over antitrust concerns. In 2015 Giphy rebuffed a Facebook offer, choosing instead to continue integrating its products with multiple social media platforms, according to news site TechCrunch.
Both companies declined to comment on any earlier talks.
Giphy will become part of Instagram, the photo-sharing site owned by Facebook. Its GIF library, which can integrate with other apps, will be further integrated into Instagram and other Facebook-owned apps, the companies said.
"People will still be able to upload GIFs; developers and API partners will continue to have the same access to GIPHY's APIs; and GIPHY's creative community will still be able to create great content," said Vishal Shah, Instagram's vice president of product, in the blog post.
"We will continue to make GIPHY openly available to the wider ecosystem," Giphy said in a post on blogging website Medium.
The American Economic Liberties Project, a Washington-based antitrust advocacy group, urged regulators to investigate and block the acquisition.
"The Facebook-Giphy merger is just the latest example of the Federal Trade Commission standing by while Facebook and Google centralize control over online communications," said Economic Liberties Executive Director Sarah Miller.
Alphabet Inc's Google acquired GIF platform Tenor in 2018 and integrated it into its image search function, which Miller said undermined the competitive market Giphy had created.
"Now, Facebook is here to pick up the wreckage, and become even more powerful," she said.
A Facebook spokesman said Giphy's current integrations with social platforms like Twitter, Snapchat and ByteDance's TikTok would not change.
The spokesman also said GIFs have no online tracking mechanisms such as pixels or cookies, a concern for privacy advocates wary of Facebook's aggressive collection of personal data for use in targeted advertising.
The Federal Trade Commission did not immediately respond to a request for comment.
Facebook's blog post said 50% of Giphy's traffic already comes from Facebook's apps, with half of that coming from Instagram. (Reporting by Elizabeth Culliford and Katie Paul; Editing by Richard Chang)