TikTok's browser can't directly open the App Store on iPhone.
Tap the ⋯ at the top right
Select “Open in browser”
Then tap “Molly for Safari”
Once you've opened it in Safari, the "Get in App Store" button will work.
Welcome to the family!
Molly is installed, and now you need to activate Molly on all websites. Follow this guide, and Molly will automatically appear when there are discount codes, reviews, and show if you can get the product cheaper.
