Study: One in four long social posts is now fully AI-written

Max Spero, CEO of Pangram, writes in a company blog post that his firm’s AI detection tool has scanned over one million social media posts since April 2026, revealing how deeply generative AI has penetrated online writing. Users of Pangram’s Chrome extension can opt in to share anonymous scan data, and the resulting dataset covers LinkedIn, X/Twitter, Reddit, Medium and Substack.

The average AI rate across all scanned posts sits at 13.8 percent, but longform content fares far worse. Across four of the five platforms, posts longer than 250 words are more likely to be AI-generated than short ones, and one in four such posts qualifies as fully AI-written.

LinkedIn is the biggest offender

LinkedIn stands out as the most saturated platform: more than 40 percent of its longform posts are fully AI-generated. Although LinkedIn posts make up only a third of all scanned items, they account for 62 percent of everything flagged as AI content. Spero points to LinkedIn’s built-in “Write with AI” feature, now rebranded “Enhance post,” as one likely driver.

X/Twitter shows the worst combined figure once mixed human-AI content is counted: only 53.2 percent of its articles are fully human-written. Substack performs best among longform platforms, though still 21.9 percent of its posts show AI involvement.

Replies stay mostly human

Reddit posts overall show the lowest AI share, just 4.4 percent, because replies are almost entirely human-written (98.1 percent). Top-level Reddit posts tell a different story, reaching 11.6 percent AI-generated content, similar to X’s top-level rate of 10 percent. On LinkedIn, top-level posts are 1.35 times more likely to be AI-generated than comments, though comments become slightly more likely when post length is controlled for.

Spero situates these findings within a broader trend: researchers estimate that 35 percent of newly published websites are already AI-generated or AI-assisted.