The US sitcom, 236 episodes of which were produced over 10 years, was added to Netflix UK at the start of this year.
The ever-popular comedy, with a cast featuring Matt LeBlanc, Jennifer Aniston and Matthew Perry, was streamed more than twice as many times as the next most popular show, Amazon’s The Grand Tour, during the first quarter of the year.
The list of most-watched SVOD (subscription video on demand) shows is found in regulator Ofcom’s Media Nations report.
The Grand Tour, starring ex-Top Gear presenters Jeremy Clarkson, Richard Hammond and James May, has led to a rise in subscriptions to Amazon Prime.
Among viewers who signed up to watch a specific show at the end of 2017, half said they had done so to watch The Grand Tour.
But while the series had a strong start, with 29% of all Amazon Prime users watching it in December 2016, a year later it was down to 22% for the second series.
Netflix had eight of the top-streamed shows, with The Crown, its lavish story of the reign of Queen Elizabeth II, in third place.
While Netflix and Amazon do not release audience figures, Ofcom said the royal drama had an average weekly reach of almost two million viewers in December 2017.
There was a 77% increase in its reach for season two during the first month of release.
Also among the top 10 are Stranger Things, the Birmingham-based crime drama Peaky Blinders, The Big Bang Theory and Vikings.
The top 10 list:
:: Friends (Netflix)
:: The Grand Tour (Amazon)
:: The Crown (Netflix)
:: Stranger Things (Netflix)
:: Peaky Blinders (Netflix)
:: Black Mirror (Netflix)
:: The Big Bang Theory (Netflix)
:: Brooklyn Nine-Nine (Netflix)
:: The Good Place (Netflix)
:: Vikings (Amazon)