Katrina, who has steered clear of all social networking sites in the past, turns 33 today.
She shared a video shot in her sea-facing apartment.
"Let`s do this," the "Bang Bang" actress said.
Dressed in white tank top and denim shorts, she also asked her fans to be "nice" and wish her on her birthday.
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Katrina uploaded a black-and-white picture of herself as the profile photo.
Over 3.6 million users have already liked her Facebook page.
The "Fitoor" actress rang in her birthday with industry friends including Alvira Khan Agnihotri, Karan Johar, Ayan Mukerji, Sultan director Ali Abbas Zafar, Kabir Khan and his wife Mini Mathur, Sidharth Malhotra, Alia Bhatt, Vikas Bahl, Aditya Roy Kapur, Abhay Deol and her manager Reshma Shetty.