How to Know If You've Been Blocked on WhatsApp

You can no longer see a contact's last seen or online in the chat window.

  You do not see updates to a contact's profile photo.

  Any messages sent to a contact who has blocked you will always show one check mark (message sent), and never show a second check mark (message delivered). 

Any attempt to place will not go through.

If you try adding that person in a WhatsApp group you will notice an error message.

If you see all of the indicators above for a contact, this could mean that the user is blocking you. However, there are other possibilities. WhatsApp has made this intentionally ambiguous in order to protect your privacy when you block someone.