Yahoo will stop letting people sign into its online services using credentials from rivals Facebook and Google.
The shift began with the Yahoo Sports Tourney Pick'Em arena and will gradually expand to all of the company's online services and products, including photo-sharing website Flickr.
"We are moving towards requiring all users to access our service with a Yahoo username over time," the faded internet search star said.
Rivalry: Yahoo will no longer support logins with Facebook or Google IDs.
"Eventually, the sign in buttons for Facebook and Google will be removed from all Yahoo properties."
Yahoo portrayed the move as enabling the California-based firm to provide more personalised services and content to visitors, but it was also seen as part of a strategy to better target money-making ads.
Yahoo is bucking a trend of websites accepting Facebook or Google usernames and passwords to allow single online identities that follow people around the internet.
Yahoo chief executive Marissa Mayer has overhauled the company's offerings and launched digital magazines as part of an effort to revitalise the ageing internet pioneer and to be at the centre of daily online habits.
She has made a priority of following people onto mobile devices, focusing on tailoring content to individual tastes while Microsoft search engine Bing does the heavy-lifting behind the scenes, crawling and indexing online content for Yahoo under the terms of a deal struck several years ago.
Meanwhile, Facebook last year unseated Yahoo as the second-place digital ad seller in the United States, according to industry tracker eMarketer.
Google remained the top digital ad seller with just shy of 40 per cent of the US market, eMarketer reported.