The 40-year-old singer said on Monday's episode of Watch What Happens Live that it was "odd" to tune into Perry's Witness special on YouTube two years after their most recent split.
"I think you have to watch all 96 hours to come to a final verdict," Mayer said when asked what he thought of the live stream. "When I see it, I think, 'That's her thing, man, to go big and bold.'"
"I checked in with it. It's definitely odd to watch your ex-girlfriend sleep," he said. "The way I see things now, I call it 'stand in the middle of the boat.' If someone says, 'I don't watch that,' it's like, yes you do."
Mayer also said he reached out to Perry to wish her a happy birthday. The "Swish Swish" singer turned 33 in October.
"I texted Katy happy birthday. It was four in the morning," he recounted. "It was like a post-midnight, haven't-gone-to-sleep-yet, it's-technically-a-birthday send. Because how weird is it to be like, 'Well, I want to say happy birthday now but I'm going wait until tomorrow afternoon.'"
Mayer and Perry called it quits in 2015 after three years of on-again, off-again dating, but have remained friendly since. Mayer confirmed in an interview with the New York Times published in March that his single "Still Feel Like Your Man" is about Perry.
"Who else would I be thinking about?" the singer said. "And by the way, it's a testament to the fact that I have not dated a lot of people in the past five, six years. That was my only relationship. So it's like, give me this, people."