What Are Hallucinated URLs?
A hallucinated URL is a web address an AI assistant gives that looks right but leads to a missing page. It happens when the model guesses a link that fits your site's pattern, or remembers a page that has since moved. In a 2025 Ahrefs study of clicked links, the six assistants averaged a likely-404 rate 2.87 times Google Search's, and ChatGPT's was about 6.7 times 1.
- Two causes: the AI invents a link that fits your URL pattern, or it cites a real page that was moved or deleted without a redirect.
- Ahrefs found the six assistants averaged a likely-404 rate 2.87 times Google's, but the average was still under 1 percent 1.
- ChatGPT had the highest rate in both Ahrefs tests, at 1.01 percent of clicked URLs and 2.38 percent of cited URLs that Ahrefs had already crawled 1.
- If a missing URL gets steady visits and a matching page exists, a 301 redirect turns lost visitors into readers 3.
What is a hallucinated URL?
A hallucinated URL is a link that an AI assistant presents as real but that does not lead to a working page. The address usually looks believable. For a plumbing firm it might be /blog/boiler-service-cost, a path that fits the site's habits but was never published.
The word comes from the wider problem of AI hallucination, where a model produces plausible but false statements. Google's own guidance on generative AI says generative models do not retrieve facts, so their output may contain inaccuracies, also known as hallucinations 2.
In practice, not every missing page is an invention. Ahrefs separates two cases. Some cited URLs once existed and were later deleted or moved without a redirect. Others are true inventions that match a site's URL pattern but never existed 1.
Why does ChatGPT give links that do not exist?
A language model predicts likely text. A URL is just text, so the model can produce one that looks right without checking it. A 2025 research paper argues that models hallucinate partly because training and testing reward guessing over admitting uncertainty 4.
Ahrefs adds that stale URLs are more likely when an assistant answers from internal knowledge instead of live search 1. A model may remember a page from an old crawl, long after you changed your site structure.
Perplexity and Gemini may track Google's own rate because they probably draw on Google's index, according to Ahrefs, while Copilot may reflect Bing's rate 1. That is the study author's suggestion, not a confirmed fact.
How often do AI assistants link to 404 pages?
Not often in absolute terms, but more often than Google. Ahrefs published the largest study we found on 2 September 2025, covering 16 million unique URLs across ChatGPT, Perplexity, Copilot, Gemini, Claude and Mistral 1. In the first test it looked at URLs real people clicked. Assistants averaged a 0.43 percent likely-404 rate, against 0.15 percent for Google, or 2.87 times as much. That figure is a simple average of six assistants, so small samples such as Mistral weigh as much as ChatGPT 1.
Ahrefs ran a second test on URLs that assistants cited in their answers, checked against its own crawler data. ChatGPT cited 404 URLs 2.38 percent of the time, against 0.84 percent for the top 20 Google results. Perplexity scored 0.87 percent, Gemini 0.86 percent and Copilot 0.54 percent 1.
Read the numbers with care. Ahrefs counted a clicked page as a likely 404 if its title contained "404" or "not found", and the author notes the method probably under-reports hallucinated links. The cited-URL test covered only the 65 percent of URLs already in Ahrefs' crawler database 1. The data is also more than a year old, so rates may have changed.
| Assistant | Unique URLs checked | Likely-404 rate |
|---|---|---|
| ChatGPT | 8,332,436 | 1.01% |
| Claude | 95,293 | 0.58% |
| Copilot | 431,319 | 0.34% |
| Perplexity | 1,133,084 | 0.31% |
| Gemini | 351,242 | 0.21% |
| Mistral (smallest sample) | 6,760 | 0.12% |
Is this the same as AI crawlers hitting 404 pages?
No, they are different problems. A hallucinated URL sends a human visitor to a missing page. A crawler 404 is a bot asking for a page that is not there.
Vercel measured the second kind in a study published on 17 December 2024. It found that 34.82 percent of ChatGPT crawler fetches and 34.16 percent of Claude crawler fetches landed on 404 pages, against 8.22 percent for Googlebot. Vercel said the bots often tried to fetch outdated assets and that the exact cause was unclear 5.
The two are linked only loosely. Both suggest AI systems hold out-of-date maps of the web. Only the first costs you a visitor, so that is the one this page is about.
What does it look like, and what should I do about it?
Here is a worked example for a made-up firm, Harbour Boilers. The numbers are illustrative. In your analytics you find that visitors arriving from ChatGPT land on a page that returns a 404. Follow the decision rule in the table.
- /blog/boiler-service-cost 18 visits/month 404 real page exists: /boiler-servicing-prices
- /blog/newsletter 11 visits/month 404 no matching page
- /pricing-2023 4 visits/month 404 old page, now /pricing
- /blog/boiler-vs-heat-pump 2 visits/month 404 no matching page
| Situation | Action |
|---|---|
| Steady visits and a clear matching page exists | Add a permanent 301 redirect to that page |
| Steady visits but no matching page | Decide whether the topic deserves a new page; until then improve your 404 page with links to your best content |
| A few visits only | Leave it, and check again next month |
| An old URL of a real page you moved | Redirect it and fix internal links that still point to it |
How do redirects capture the lost traffic?
A 301 redirect tells browsers and search engines that a page has moved for good. Google says the 301 and 308 status codes mean a page has permanently moved, and recommends a permanent redirect when you are sure it will not be reverted 3. Visitors who follow a bad AI link then land on a useful page instead of an error.
Ahrefs suggests a practical routine. Filter analytics to AI-assistant traffic, check the HTTP status of those landing URLs, keep the ones that return 404 and get visits, and confirm each is a hallucination and not a broken real page. The author used more than 10 visitors a month as a cut-off. If a relevant page exists, redirect it. Otherwise, improve the 404 page 1.
To separate AI visits in Google Analytics 4, use the AI Assistant default channel. Google's help page says it groups visits from sources such as ChatGPT, Gemini, Copilot and Grok, and that it excludes AI Overviews and AI Mode, which count as Organic Search 6. Our guides on capturing hallucinated URLs with 301s and tracking AI traffic in GA4 walk through the setup, and the AI 404 Redirect Builder writes the rules.
What do people get wrong about hallucinated URLs?
The first mistake is to redirect every missing URL to the home page. That sends visitors somewhere they did not ask for, so redirect only to a page that answers the same need.
The second is to treat this as a big traffic source. The Ahrefs rates are small, and the traffic from AI assistants is itself small for most sites, as our page on how much traffic ChatGPT sends shows. The fix costs little, but it is not where your growth will come from.
The third is to assume the URL was invented when it may be an old page of yours. Check your own history first. A missing redirect after a site rebuild is the easiest cause to fix, and Ahrefs notes that some missing pages once existed 1.
What an AI assistant searches when it answers this
We gave the question below to AI search tools and recorded the web searches they ran behind the scenes. This is called query fan-out. Each phrase is a page you could publish to be found and cited.
“why does ChatGPT link to pages that do not exist”
The searches it ran- why ChatGPT gives broken links hallucinated URLs
- ChatGPT citations 404 pages study
Frequently asked questions
Why does ChatGPT link to pages that do not exist?
How common are broken AI links?
Rare per click, but more common than with Google. Ahrefs found an average likely-404 rate of 0.43 percent for assistants against 0.15 percent for Google, and 1.01 percent for ChatGPT 1. The data comes from 2025, so current rates may differ.
Should I redirect every hallucinated URL?
No. Redirect the ones that get steady visits and have a clear matching page. Ahrefs used more than 10 visitors a month as its cut-off 1. For the rest, improve your 404 page so a lost visitor can still find something useful.
Is a hallucinated URL the same as a broken link on my site?
No. A broken link is a mistake on a page you control. A hallucinated URL is an address an AI produced, which you did not publish. The fix for both is often a redirect or a corrected link.
Can I stop AI assistants inventing links to my site?
Not fully. You can reduce stale links by keeping redirects after site changes, using clear and stable URL patterns, and publishing pages for questions buyers ask. You cannot control what a model writes.
Sources
- New Study: How Often Do AI Assistants Hallucinate Links? (16 Million URLs Studied) · AhrefsOpened October 20, 2026. Supports: 404 rates per assistant in two tests (2.87x Google; ChatGPT 1.01% and 2.38%), method and limits, outdated versus invented URLs, redirect routine with a 10-visitor threshold. Published 2 September 2025.
- Google Search's guidance on using generative AI content on your website · Google Search CentralOpened October 20, 2026. Supports: Generative models do not retrieve facts and may produce inaccuracies, also called hallucinations; generating many pages without adding value may violate the scaled content abuse policy.
- Redirects and Google Search · Google Search CentralOpened October 20, 2026. Supports: 301 and 308 mean a page has permanently moved; use permanent redirects when sure they will not be reverted.
- Why Language Models Hallucinate · arXiv (Kalai, Nachum, Vempala, Zhang)Opened October 20, 2026. Supports: Training and evaluation reward guessing over admitting uncertainty, producing plausible but incorrect statements. Submitted 4 September 2025.
- The rise of the AI crawler · Vercel (with MERJ)Opened October 20, 2026. Supports: 34.82 percent of ChatGPT crawler fetches and 34.16 percent of Claude crawler fetches were 404s, against 8.22 percent for Googlebot; cause unclear. Published 17 December 2024.
- [GA4] Default channel group · Google Analytics HelpOpened October 20, 2026. Supports: The AI Assistant channel groups visits from sources such as ChatGPT, Gemini, Copilot and Grok, and excludes AI Overviews and AI Mode, which count as Organic Search.