What is does snapchat notify when you open a chat?

Yes, Snapchat does notify the sender when you open a chat. This means that if you receive a message from your friend and open it, they will receive a notification saying "Opened" or "Read" next to the message. This feature was designed to provide transparency and encourage timely responses to messages. However, if you don't want the sender to know when you've read their message, you can turn off this feature by going to your settings and disabling the "Send Read Receipts" option.