1/6: Taylor Swift turned a year older on December 13. / Image: Blake Lively/Instagram

2/6: Recently, her best friend Blake Lively penned a heartfelt note for the pop singer. / Image: Blake Lively/Instagram

3/6: She also shared unseen photos from the birthday bash. / Image: Blake Lively/Instagram

4/6: The best friends twinned in black outfits. / Image: Blake Lively/Instagram

5/6: Among the guests were Sabrina Carpenter, Blake Lively and Gigi Hadid among others. / Image: Blake Lively/Instagram

6/6: The caption read, "Somehow, she’s even better in real life. Happy, happy birthday to the one and only." / Image: Blake Lively/Instagram