In November 2022, OpenAI released ChatGPT to the public. Less than four years later, a study published August 20 by Pew Research Center's Data Labs offers the first large-sample quantified answer to a question that has hung over the web ever since: how much online content is now written by AI? The answer is more aggressive than most people's intuition.

490,000 webpages, one detection model

The team drew roughly 490,000 English-language webpages from Common Crawl snapshots spanning January 2021 to July 2026 — deliberately starting a couple of years before ChatGPT's release so the before-and-after comparison has a baseline. The detection tool is Open Pangram, an open-weight AI detection model built by Pangram, which looks for statistical patterns in language — words, phrases and linguistic quirks — to flag pages "written or substantially edited by AI."

One honest caveat the researchers themselves stress: AI detection models are not perfect and can misclassify individual documents. But at the scale of hundreds of thousands of pages, the aggregate statistical trend holds.

Two numbers: one in ten, and one in three

In a random sample of 10,000 webpages from the July 2026 crawl, 10% showed significant signs of AI authorship. That sounds modest — but the internet is a mix of old and new material, and plenty of pages in the sample physically could not have been written by AI.

Filter out the old pages and look only at content published after ChatGPT's release, and the number jumps to over one-third. Pew also notes this is in line with other studies collected at ai-on-the-internet.github.io — not an outlier.

.com is the hotspot; .edu and .gov hold the line

When ChatGPT first launched, AI-typical language patterns appeared at similar rates across .com, .org, .edu and .gov. By 2026 they had diverged sharply: around one-in-ten .com pages show AI signs, roughly double the rate on .org (4.6%) and ten times the rate on .edu and .gov (both around 1%). Commercial content production has embraced AI in bulk, while academic and government editorial pipelines still act as a firewall.

The trend shows no sign of slowing: AI-sign prevalence on .com climbed from 1.09% in early 2021 to 9.35% by early 2026.

AI's stylistic fingerprints are all over the corpus

Comparing today's web to a 2023 snapshot, Pew's list of stylistic shifts reads like an AI-writing identification checklist:

  • Em dashes appear about twice as frequently (5.79 to 11.19 per 10,000 words);
  • Oxford commas are up 63% (34.04 to 55.51);
  • AI-favored words like "delve," "interplay" and "testament" have more than doubled (11.94 to 26.02);
  • "Not just X, it's Y" negative parallelism has nearly tripled (0.87 to 2.36).

Pew even publishes the full vocabulary list: additionally, crucial, fostering, landscape, tapestry, underscore, vibrant... anyone who reads English blog posts will recognize the register.

My take

The truly sobering part of this study is not how much of the web is AI-written, but where those pages go next. AI models learned these stylistic preferences from human-written training data, and those preferences are now flowing back onto the web at doubling rates — the loop between training corpora and generated content is tightening. Detector error rates, plus humans actively imitating these constructions (yes, people now write like AI too), will keep blurring the line between "AI signs" and "AI-generated."

For model developers, data cleaning just got another justification; for content platforms, the 10x gap between .com and .edu shows that editorial review remains the most effective quality control we have. Next time someone argues about whether the internet will fill up with AI content, hand them this study: it is not a future scenario — it already happened, just far more unevenly than expected.

Source: Pew Research Center, How Much of the Internet Is Written With AI?, Aug 20, 2026.