The American star's match will though be the first of this year's tournament held behind closed doors as France still has a 9pm curfew in place due to Covid-19.
For her coach, Patrick Mouratoglou, there's no comparison between Williams's achievements and those of Court, who won 13 of her titles when tennis was still an amateur sport.
"The Aussie crowd is so amazing, so it was nice to see," Williams, sporting a "Queen" necklace, told reporters.
"The difference today was errors," Williams said earlier in her news conference. "Honestly, it was opportunities where I could have won. I could have been up 5-Love. I just made so many errors.
World number two Halep is no slouch around the court, and the pair shared 52 rallies of five shots or more during a heavyweight contest on Rod Laver Arena.
"I think 1926, the summer of 1926 I think was the last time I felt that," the 39-year-old smiled.
The Japanese three-time Grand Slam champion overcame the Taiwan world number 71 unorthodox style 6-2, 6-2 in an all-Asian quarter-final at a crowd-less Rod Laver Arena.
Sabalenka won three straight games to get back on terms but Williams's experience saw her through as she maintained her unbeaten run since emerging from 14-day quarantine in Australia.
Kvitova, the former Wimbledon champion and Melbourne runner-up in 2019, committed 44 unforced errors in her 6-4, 1-6, 6-1 defeat to Romania's Sorana Cirstea.
American Williams has been stuck on 23 majors since triumphing at Melbourne Park in 2017, losing four Grand Slam finals since to remain one short of Margaret Court's record.
I felt really comfortable in the tournament leading up to this just a couple days ago when I was playing.
"There was a lot of things I was struggling with, and I feel like during quarantine I really had to dig deep in myself and try to figure it out for myself."
Simona Halep is the only woman over the age of 24 to have won a Grand Slam singles title in the last two years.
While Osaka played only four tournaments last season, Barty holds the top ranking despite playing her first competitive matches in almost a year in the Australian Open warm-ups this week.
Osaka then lifted her intensity, opening to a 4-0 lead before Boulter unexpectedly peeled off three straight games. But the Japanese star refocused to force a deciding set, which she ran away with.
The 26-year-old Ukrainian, who has never reached the final of a Grand Slam, played her first match in Melbourne since emerging from the 14-day mandatory quarantine.