Instagram introduced the Stories format before Facebook adopted it in 2017.
Instagram Stories launched in August 2016. The feature allowed users to post photographs and videos that ordinarily disappeared after 24 hours, creating a temporary stream separate from the permanent grid of profile posts.
Instagram’s Stories design closely resembled Snapchat’s disappearing-post format, and the feature quickly became a major part of Instagram’s product. Facebook then introduced its own Stories feature in 2017, followed by similar formats in Messenger and WhatsApp.
The answer is Instagram, not Snapchat, even though Snapchat pioneered the broader disappearing-story concept. Instagram was already owned by Facebook at the time, following Facebook’s completed acquisition of the photo-sharing company in 2012. Meta later used Stories across several of its apps.