Due to privacy rules, WhatsApp does not directly notify you that a user has blocked you. However, you can make sure that you have been blocked by following some tips provided by the application.
1. Profile Picture and Status Information
You can no longer see the profile picture of the person who blocked you; Instead, a default blank profile icon appears. Additionally, the user's "About Me" status or last seen information is completely hidden.
2. Double Tick Mark (Delivered Information)
When you are blocked, the messages you send will not reach the other party. There will always be a single gray tick next to the messages you send, and never a double gray or blue tick.
3. Search Attempts
Try voice or video calling the suspicious person via WhatsApp. If the call always stays in "Searching" status and never moves to "Ringing", you may have been blocked.