Post decay

Post decay is the rate at which a post’s engagement falls off after publishing — typically capturing 80% or more of its lifetime engagement within the first 24 to 48 hours on most platforms.

Decay curves vary by platform. Instagram feed posts decay fastest (most engagement in 12–24 hours); LinkedIn posts have longer tails (48–72 hours, sometimes longer for newsletter-format content); blog posts on a site with steady search traffic have the slowest decay (engagement spread over months). TikTok and Reels can have very long tails when the algorithm picks them up post-publish.

The practical implication: most engagement is decided by what happens in the first few hours after publish. Posting time, first-hour engagement, and the algorithm’s initial distribution call largely determine the post’s ceiling.

Brands that don’t understand decay curves either over-invest in long-after-publish promotion (low ROI) or under-invest in launch-day engagement (where the leverage actually is).