Whoever taps your link inside Instagram or TikTok lands in those apps' in-app browser, not signed in — they don't subscribe, follow or buy with one tap. Paste the link here and it will open in the native app, where the person is already signed in.
Without an account, the link works but counts nothing. With an account, you see how many taps it got, from which country and which device — which is how you know if it's worth it.
On Android, the link uses the system's intents mechanism, with automatic fallback to the web: if the app is installed it opens in the right place; if not, the person lands on the normal page without seeing any error.
On iPhone, it uses each app's own scheme with a timed fallback: it tries to open the app and, if nothing happens within a fraction of a second, sends the person to the web version. Nobody is left hanging on a blank screen.
In the app, your follower is signed in, with history and subscriptions. In another social network's in-app browser they're an anonymous stranger: the subscribe button asks for a login, and almost nobody types a password for a video. The interest was there — the friction killed it.
We wrote about this in detail in Instagram's in-app browser and in the guide to making your bio link open in the YouTube app.