[rohug]

Worth noting WhatsApp also provides link previews now. Although it is supposedly e2e communication, the link previews are likely generated by reaching out to a similar facebook unfurl service.

They can then have a single map of phone num -> links rendered between fb and whatsapp.

[yawaramin]

WhatsApp fetches a link preview on the sender's device before the message is encrypted, and packages it up with the message before sending. Depending on how exactly they implement the fetch, they may or may not know what links you sent.

[Sami_Lehtinen]

At least links in PDF over WA didn't get visited from FB servers. I just personally tested it moments ago.

[Thorrez]

What's visiting the links? Your phone?

[exadeci]

Try sending a link immediately and you'll see that it doesn't get a preview.

Give it a few second after pasting it and you'll get the preview, because it gets it from your device.

[imanobody]

WhatsApp also scans pdf files you send to a contact. Easy to confirm as well: get some random pdf with chinese filename and chinese content. Send it to a contact. Watch the delay in send/receive. Now do the same for any random pdf that's all English. Watch the regular send/receive time occur.

The only conclusion: it takes a little time for a file that's flagged - based on its language - to pass the scanners?