The link preview is generated locally, but Whatsapp blacklists domains it doesn't want previews to be generated for by marking them as 'bad domains' in the app.

The link preview is generated locally, but Whatsapp blacklists domains it doesn't want previews to be generated for by marking them as 'bad domains' in the app. It did this for telegram a few years ago, and an analysis of the android app's source code proved it was intentional. https://www.androidpolice.com/2016/09/09/whatsapp-is-blocking-telegram-links-in-the-android-app/ https://www.androidpolice.com/2016/09/09/whatsapp-is-blockin...