The other person won't know that you've taken a screenshot of an image, message, or anything else they've shared on Instagram ...

Nor does Facebook. When does Instagram notify about a screenshot? The only time Instagram notifies users that someone has taken a screenshot is in very specific direct message conversations.

MarketWatch lets users subscribe to Web notifications. These types of alerts allow websites to send users updates or advisories. These notices can be sent to a computer if a user has granted ...