Prior to any public bad blood, Perry and Swift appeared to be friends. The duo often spent time together at award shows and celeb events, like at the Grammy Awards - Salute to Icons Honoring Doug Morris event in Jan. 2010.
Before releasing her album 1989, Swift did an interview with Rolling Stone. In the 2014 interview, T.Swift hinted at a feud with a fellow female artist, not saying Perry's name specifically.
While explaining the story behind "Bad Blood," a song featured on 1989, Swift shared, "For years, I was never sure if we were friends or not."
That changed, Swift said, when the woman "did something so horrible."
"I was like, 'Oh, we're just straight-up enemies.' And it wasn't even about a guy! It had to do with business," T.Swift told RS. "She basically tried to sabotage an entire arena tour."
Shortly after the interview was released, Perry infamously tweeted, "Watch out for the Regina George in sheep's clothing..."
In "Bad Blood," Swift addresses the feud—still not naming names. "Oh, it's so sad to/Think about the good times/You and I," the lyrics state. "'Cause, baby, now we've got bad blood/You know it used to be mad love."
In May 2015, T.Swift dropped the star-studded music video for the track, featuring Kendrick Lamar, Selena Gomez, Gigi Hadid and more celebs.
In May 2017, Perry released a new song called "Swish Swish," featuring Nicki Minaj. The track's lyrics—which include a sheep reference—sparked theories that the song is about Swift.
When asked who the track is about, Perry replied, "I think it's a great anthem for people to use whenever somebody's trying to hold you down or bully you."
That same month, Perry addressed her feud with Swift during Carpool Karaoke with James Corden. During her chat with the late-night host, Perry said she's ready for the feud "to be done."
She went on to add, "I think personally that women together, not divided, and none of this petty bulls--t, women together will heal the world."
In May 2018, a year after the release of "Swish Swish," Perry sent Swift an actual olive branch ahead of her Reputation Stadium Tour kickoff.
"So I just got to my dressing room and found this actual olive branch," Swift said in an Instagram video at the time. "This mean so much."
Swift captioned the video, "Thank you Katy."
Perry and Swift appeared together in the "You Need to Calm Down" music video, dressed as a burger and fries.
"The ending of the video is actually pretty emotional," Swift shared on the Heart Breakfast radio show. "Katy Perry is in the video and she and I definitely like have been on very good terms lately, but I don't think anybody knew it, 'cause we just kind of reconnecting privately and just wanted to make sure that everything was really good with us and that it was like a very real before we let anyone know, like, we're not only good but we're friends again."
T.Swift added, "So it was really wonderful to get to sort of unveil it to the world in like a cheeky sort of fun way. But it ends up being sort of emotional."