Knowing the age of cited pages could help explain whether AI favors fresh content. First, we wanted to establish how much of that age can actually be measured from the available evidence.
We examined 8,215,946 citations from ChatGPT Search and Google AI Mode between May 24 and August 28, 2026. We checked available Last-Modified dates and applied reliability filters before estimating page age, keeping the unmeasurable portion visible.
A fresh date can hide unchanged content. We could estimate modification age for just 1.4% of citations, leaving most major platforms out. Focus updates on the prices, capabilities and facts buyers need.
The missing pages change what this study can answer
Of 8.2 million citations, only 116,379 passed every age filter. Eleven of the fifteen most-cited websites had no measurable citations. YouTube, Reddit and several other major platforms did not supply usable modification dates through this method.
The measurable slice therefore cannot tell us the typical age of every page AI cites. It mostly describes the sites whose servers exposed dates we could use.
An old page can contain new information
Publication date tells you when a page first appeared. A substantive update tells you when its facts changed. The Last-Modified header is a date reported by the server; it can also change because of a rebuild or template update.
For a pricing page, a changed plan limit matters to a buyer. A new footer date may not. Keep those events separate when deciding whether content needs a refresh.
The measurable subset was weighted toward recent modifications
Within the filtered subset, 65.3% of citations pointed to pages whose reported modification date was within a week of the answer. The median was three days. At the other end, 6.4% pointed to pages reporting a modification more than a year earlier.
These are reported modification ages, not verified publication ages or evidence that refreshing a page earns citations.
Measurable citations by server-reported content age
- 0-7 days65.3%75,995
- 8-30 days15.3%17,857
- 31-90 days6.8%7,948
- 91-180 days3.4%3,934
- 181-365 days2.8%3,253
- 1-2 years2.8%3,208
- 2-5 years2.2%2,607
- Over 5 years1.4%1,577
Server dates can look fresh even when the content is unchanged
Among pages with a parseable header, 31.8% stamped it within two minutes of our fetch. Those dates can describe when a response was generated rather than when a writer changed the page. We excluded them from the age calculation.
Other pages had already changed again before our crawler arrived, leaving no usable view of the page’s modification date at the time of citation. Even the oldest surviving dates included apparent header errors.
Refresh the facts buyers depend on
Prioritize changed prices, product capabilities, compatibility requirements and availability. Preserve accurate evergreen explanations. A fixed publishing cadence is less useful than knowing which facts have become stale.
For a meaningful update, save the old and new text and follow the same buyer questions afterward. Check whether answers adopt the new fact and whether they cite the updated page. That is a clearer measure of progress than lowering a page-age number.
How we estimated page age
We excluded serve-time stamps, modification dates after the answer, missing later crawls, crawl gaps over 45 days, and implausible dates. A stricter header rule gave a four-day median; using pages with a single header observation gave six days. These checks describe the same selected population, not the missing platforms.
Last-Modified remains a server claim. This analysis does not establish a preferred content age or an uplift from updating a page.
How we measured
We analyzed 8,215,946 citations across 3,486,814 cited pages in 787,107 answers to 18,308 organic prompts on ChatGPT Search and Google AI Mode from May 24 through August 28, 2026. Of those citations, 1,183,499 pointed to pages that returned a usable Last-Modified header, and 116,379 passed every reliability filter and could be aged.
- citations passed the age filters
- 116,379
- median server-reported modification age
- 3 days
Only within the measurable subset
- most-cited websites had no measurable citations
- 11 of 15
Get the data
Sources
- Ahrefs: Do AI assistants prefer to cite fresh content? · accessed August 29, 2026
- Ahrefs: How long does it take to rank in Google? And how old are top ranking pages? · accessed August 29, 2026
- MDN Web Docs: Last-Modified header reference · accessed August 29, 2026
- Thompson: Improved methodology for longitudinal Web analytics using Common Crawl · accessed August 29, 2026