To know if someone blocked you on WhatsApp, you can look for these signs:
- You cannot see their profile picture or any updates to it.
- Their "last seen" or "online" status is not visible to you anymore.
- Messages sent to them only show one gray checkmark (sent but not delivered).
- You cannot see their status updates.
- Calling them via WhatsApp does not go through or ring.
- Trying to add them to a WhatsApp group results in an error or they don't appear in the group after adding.
Additionally, if you tap on their profile picture and it disappears, that strongly indicates blocking, as the app refreshes the profile image and removes it if you are blocked. None of these on their own is definitive (some could be due to privacy settings), but if several apply, you are likely blocked.