Open the TikTok app and go to your profile
Tap the three-line menu (or the hamburger icon)
Select Settings and privacy
Tap Privacy
Tap Profile personalization
Turn on “Personalize your profile” (if you see this option)
Tap Edit profile
Update your birthday in the “Date of birth” field (if available)
Save your changes
If you don’t see a way to edit your date of birth, submit an age-related request in the app: Settings and privacy → Report a problem → Account settings (or similar) → Age/Date of birth
Follow the prompts and submit the required info or verification details
Wait for TikTok to review and confirm the change