I think part of TikTok's success is the fact that they have a public/guest browser platform[0] that doesn't restrict you from seeing content without an account. It means people who wouldn't usually have the mobile app can still be a part of the action, and that may eventually drive them to sign up.
It's actually almost unbelievable that you can browse endlessly and never once be prompted to sign up unless you try to engage in some way. Instagram, Reddit, Twitter etc all bother you from the very second you load the page with modals and banners bullying you into signing up or getting their mobile app, if they let you see anything at all.
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