Do AI Crawlers Render JavaScript? What Your Brand Loses When They Don't
Most AI crawlers fetch raw HTML and skip your JavaScript. A 37,927-journey study finds agents that can't read a site build answers from other sources, recommend it about half as often, and get its facts wrong more. Here's what that means, and which pages to check first.
Frequently asked questions
Do AI crawlers render JavaScript?
Mostly not, on the best published evidence. Vercel and MERJ's December 2024 analysis of crawler traffic across Vercel's network found that OpenAI's, Anthropic's, Meta's, ByteDance's, and Perplexity's crawlers fetch HTML without executing JavaScript, while Google's Gemini crawler and AppleBot render pages fully. OpenAI's bot documentation says nothing either way, and no AI vendor had publicly announced JavaScript rendering as of October 2026.
Has ChatGPT started rendering JavaScript?
There is one unconfirmed report. A developer logged OpenAI's OAI-SearchBot jumping from about 1,250 requests a day to 41,444 on 25 September 2026 on five sites on one server, with request patterns consistent with pages being rendered. OpenAI has not announced a change. Treat it as a signal to watch, not a reason to stop serving content in raw HTML.
Does it matter for Google AI Overviews if my site relies on JavaScript?
Less than for other engines. Google says Googlebot queues every indexable page for rendering in headless Chromium, and its AI features are built on its core Search systems. The same Google page still recommends server-side or pre-rendering because not all bots can run JavaScript.
What happens to AI answers about my brand if agents can't read my site?
In a September 2026 preprint covering 37,927 agent journeys about 1,056 businesses, answers about not-agent-ready sites drew 58% of their content from the business's own pages against 78% for agent-ready sites, doubled their reliance on web search, and clearly recommended the business 11% of the time against 20%. The model filled the gap with other people's pages, not with training knowledge, which stayed at 7–10% either way.
Do agents make things up when they can't read a site?
Mostly they leave things out. In the same preprint, the share of requested facts never mentioned rose from 29% in site-built answers to 45% in web-built ones, while facts stated wrongly rose only from 4% to 6%. Answers containing none of the requested facts were 3.7 times more common when the agent built them from the web.
How much of a typical page is only visible after JavaScript runs?
Not much at the median. HTTP Archive's 2025 Web Almanac found the median home page has about 12% more words after rendering than in its raw HTML, and inner pages 11.5%. The risk sits in the tail: single-page apps, pricing tables loaded from an API, and tabbed feature pages where the key facts are exactly the part that renders late.
If AI citations mostly come from third-party sites, why does my own site's readability matter?
Because the two findings measure different questions. Citation studies of category prompts find most citations point at domains the brand does not own. The agent study only asked questions that already named the business's domain, about pricing, features, and setup. Third-party presence decides whether you get named; your own site's readability decides what the agent says once it goes to check.