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.

Step 1: Open WhatsApp.

Step 1: Go to iPhone Settings.

Darker screens also use less power. Finally, it just looks cool, and makes a refreshing change from all-white interfaces. It's always good to have more options.