How can I tell if someone has blocked me on Coco?

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). It’s an indicator that person has blocked. However, there are other possibilities. We have made this intentionally ambiguous in order to protect your privacy when you block someone. Thus, we cannot tell you if you are being blocked by someone else.

Related article: How to block someone on Coco?