Swift shared a sweet pic of the model, but also seen in the pic is the "Blank Space" singer's boyfriend Calvin Harris. The image shows Kloss cooking up some food on the stove.
"Some of my best times are with her, laughing in the kitchen," Swift wrote. "Happy Birthday to the ray of light that is @karliekloss!"
The 25-year-old singer seemed to actively avoid mentioning the other "ray of light" in her life, Harris, who appeared to have no idea this photo was being taken! Seriously, just look at that thousand-yard stare.
Karlie turned 23 on Monday, and the gorgeous Victoria's Secret model celebrated by baking herself a cake, which she documented in a short video on Instagram.
Swift and Kloss have been BFFs for some time. The dynamic duo appeared together on the cover of Vogue earlier this year, and Kloss was also one of the famous friends in Swift's "Bad Blood" music video. Swift even worked the runway with Kloss at the Victoria's Secret Fashion Show in 2014.
Here's a look at Swift's other besties, and how they stack up against the newly 23-year-old model.