Festival organiser Emily Eavis said it was "lovely" to welcome the first revellers into Worthy Farm in southwest England with her dad, Michael, who founded the event in 1970.
The 2025 edition sold out in 35 minutes, before any headliners were announced. The festival will take one of its periodical "fallow" years in 2026 to reduce the environmental impact on the dairy farm.
"It is always a huge celebration when we go out for the fallow year," Emily Eavis told Reuters.
"You can really feel it in the areas and all of the festival-goers wanting to eke out every last second of it."
Pop rock band The 1975 will headline the main Pyramid Stage on Friday, while Neil Young tops the bill on Saturday.
Rod Stewart, 80, will take the coveted legends slot on Sunday afternoon and 22-year-old US singer Olivia Rodrigo closes the show on the biggest stage later that evening.
Stewart has also turned his hand to designing a giant boombox-shaped toilet for the festival. WaterAid's Boombox Bog houses a toilet that sits behind the tape deck of a giant blue boombox decorated featuring a leopard print, a pattern often worn by the veteran rocker.
Festival-goers will be able to hear some of Stewart's hits from the Boombox Bog including Da Ya Think I'm Sexy? and Sailing while also listening to water-themed messages from the singer.
Among the list of acts will be Irish rap group Kneecap, performing days after one of its members was charged with a terrorism offence for allegedly displaying a flag in support of Iran-backed militant group Hezbollah.
Britain's Prime Minister Keir Starmer told the Sun newspaper it was "not appropriate" for the group to appear.
Liam O'Hanna, whose stage name is Mo Chara, is alleged to have waved the flag during a gig in London in November 2024.
The group is due to perform on the West Holts stage on Saturday afternoon.
with PA
