The defending champion won 6-2 7-5 6-2 under the roof on Rod Laver Arena at a rainy Melbourne Park.

The Swiss third seed, 37, is aiming to become the first man to win seven Australian Open titles.

Next up for him is Greek 14th seed Stefanos Tsitsipas, who beat Nikoloz Basilashvili 6-3 3-6 7-6 (9-7) 6-4.

Joining Federer in the next round is Czech former semi-finalist Tomas Berdych, who knocked out Argentine 16th seed Diego Schwartzman 5-7 6-3 7-5 6-4.

Unseeded Berdych, who beat Britain's Kyle Edmund in the first round and has found his form after an injury-hit 2018, will play the winner of Friday's match between world number two Rafael Nadal and Australian Alex de Minaur.

Federer serves up victory in style

The Swiss was in a ruthless mood from the start, breaking Fritz's second and third service games on his way to a 5-1 lead.

But it was on his own serve where the 20-time Grand Slam champion dominated, with Fritz taking just two points on the Federer serve in the first set.

He sealed the set with an ace with just 20 minutes on the clock and carried on where he left off in the second with back-to-back holds to love.

But the 21-year-old American began to apply a bit more pressure on Federer's serve midway through the second, taking him to deuce in the eighth game before losing his own serve three games later.

From there Federer served for the set, once again wrapping it up with an ace - the eighth of his 10.

Back-to-back breaks in the third sealed the fate of Fritz, who had shown glimpses of a promising future with his shot-making as well as an ability to laugh at himself when he fluffed an easy smash.

"I wanted to get out the blocks quickly as I knew of the threat and his possibilities on the serve," said Federer, who was playing his 100th match on the Rod Laver Arena.

"The second set was tough. There were a few chances but he protected his serve well and it was close. We had some good points and it was fun. I wish him all the best for the future."