From Saturday, SA has scrapped all density limits in hospitality and other venues, along with removing capacity caps on household gatherings.
Singing and dancing is now allowed in all settings while most people who contract coronavirus will only be required to isolate for seven days, down from 10.
People with serious underlying health conditions may be required to isolate for longer, but will be guided by health officials.
Mask mandates for indoor venues remain in place but will be reviewed next week.
Adelaide Fringe Director Heather Croall said the changes meant audiences could increase, something venues and artists are thrilled about.
"The whole Fringe experience is about going out for a meal, seeing a show and dancing afterwards, so we are welcoming of these changes," she said.
"And with hundreds of shows already sold out over the next 10 days, the increased capacity will mean that more audiences can get out there and buy tickets."
SA's COVID-19 daily case numbers have hovered around 2500 over the past few days and were expected to remain at those levels for the immediate future.
On Friday there were 2503 new infections reported, along with one death.
There are 88 people with COVID-19 in hospital including 10 in intensive care, where two are on ventilators.
Active cases across the state stand at 22,054.
Premier Steven Marshall said the changes to virus rules were only possible thanks to the great co-operation of the state's public.
"Overall South Australia has come out of this extraordinarily well compared to just about any other jurisdiction in the world," he said.
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