You are opening Instagram? Now that social media service tells your friends who are online.
Your friends who happen to be equally opening Instagram will be marked with a green dot next to her photo. This can be displayed in the direct messaging menu (Direct Messages) and from your friends list.
Green point indicator is intended to facilitate Instagram users to communicate with each other, by sending direct messages. Instagram users who are online will certainly be more responsive to the messages you send.
This indicator is not shown for everyone, only for people who follow you (follower), as well as people who have conversed with you through direct messages.
This online indicator feature may remind you of traditional instant messaging apps on your computer, such as Yahoo Messenger (which is now deceased) or Google Talk / Hangouts. The difference is that in instant messaging applications like this, we not only know someone is online, but also let us know that we are busy, do not want to be contacted, or are online but not near the computer / mobile phone.
Surely not everyone is comfortable telling everyone online status. Sometimes we just want to open Instagram to look at the photos and pictures of the people who followed, but not in the mood to chat and socialize.
Fortunately Instagram also provides a setting to disable the green dot indicator. This can be done by turning off the “Show Activity Status” setting in the Privacy and Security section (privacy and security).
According to Instagram blog post, this feature has been active since July 19, 2018 ago. If you have not found it yet, you may need to update the Instagram app to the latest version.
Source: Instagram Press Blog