Previously, 29 players had shot 63 in a major championship (31 rounds), but no one had gone any lower in a men’s major.
Grace shot 8 under on the par-70 links and didn’t make a bogey. He put himself in position for the record with a two-putt birdie from 35 feet on the par-5 17th.
“It was a special day,” Grace said afterward. “I had no idea that was the lowest at all. I was so in the zone, was trying to finish the round without a bogey.
“Sometimes it helps not knowing these things.”
The previous low round at Birkdale was 63, shot by Jodie Mudd in the final round of the 1991 Open. On Friday, in blustery conditions, Birkdale surrendered just eight under-par scores all day.
With temperatures in the mid-60s and little wind, Grace went out in 29 and then added birdies on the 13th and 14th holes to close in on one of the most hallowed marks in golf. He drained a 40-footer on 16 for an unlikely birdie, then tacked on another birdie on 17. His two-putt par, from behind the green, on the final hole secured his place in the history books.
Grace said the greens, during the championship's first day without rain and high winds, were running faster than the previous two rounds, and he was very comfortable on them.
"I wasn't thinking about my stroke," he said. "When you go on a run like that, you stop thinking about golf.
"It was a special day."
For more on Branden Grace's historic round visit TheOpen.com