Cats.txt
vs LLMs.txt: I Ran the Experiment So You Don't Have to Trust Your GEO Horoscope
I uploaded a file called cats.txt
to a website. It had no real instructions. No SEO value. Nothing technical inside
it at all.
AI engines treated it exactly the same
as sites using the "official" llms.txt file.
That's when it hit me: a lot of us
aren't doing SEO. We're reading horoscopes and calling it strategy.
What Is llms.txt —
And Why Everyone Suddenly Believes in It
llms.txt is a simple text file website
owners add, hoping it tells AI models like ChatGPT and Gemini how to
"read" their site. The promise sounds great: control how AI sees
your business.
It spread fast, the way meta keywords
once did. Back then, marketers stuffed keywords into a hidden tag, convinced it
boosted rankings. Google quietly stopped using it years ago. Most people kept
doing it anyway, just in case.
llms.txt has that same energy:
unproven, but too tempting to ignore.
The GEO Horoscope
Effect
Horoscopes work because of something
called a Barnum Statement — vague lines so general they feel personal.
"You're strong, but sometimes doubt yourself." That fits almost
anyone.
GEO (Generative Engine Optimization)
advice often does the same thing. "Add llms.txt to get cited by AI" sounds
specific. It isn't. It's vague enough that when it "works," people
assume it caused the result.
Here's the trap: if your site gets
cited by ChatGPT after adding llms.txt, you credit the file. You ignore
every site that got cited without one. That's not evidence. That's confirmation
bias wearing an SEO hat.
The Cats.txt
Experiment
To test this, I built a file with the
same format as llms.txt — but filled it with nonsense. Cat facts. No real AI
instructions. I named it cats.txt and placed it on a live site.
Then I watched how AI crawlers
responded.
Nothing changed. The site got
crawled, read, and treated the same way as sites running a "real"
llms.txt file. No boost. No penalty. No special treatment either way.
If llms.txt genuinely worked as
marketed, a fake file should have flopped. It didn't.
The Placebo Protocol:
Two Identical Sites, One Real Test
To go further, I built two nearly
identical simple websites.
- Site
A:
had an llms.txt file
- Site
B:
did not
Same content. Same structure. Same
topics. I tracked which one got cited more across ChatGPT, Perplexity, and
Gemini over several weeks.
The result: no meaningful
difference. Citations were inconsistent on both sites, driven far more by
content clarity than by the presence of a text file.
If llms.txt worked the way it's
marketed, these twin sites wouldn't have looked so identical in AI results.
So Should You Delete
Your llms.txt File?
Not necessarily. There are narrow cases
where it might genuinely help — very large, complex sites where giving AI
crawlers a clean map of key pages adds real technical clarity.
But for most small businesses and
blogs, it isn't magic. It's not doing the heavy lifting people assume.
What actually seems to influence AI
citations:
- Clear,
well-structured content that directly answers real
questions
- Genuine
topical authority built over time
- Content
that's easy for both humans and machines to understand
llms.txt isn't useless. It's just overhyped
— the SEO equivalent of a lucky charm.
Key Takeaways
- llms.txt
has no proven, consistent impact on whether AI engines cite your
site.
- The
Cats.txt Experiment showed a meaningless fake file was treated
identically to a "real" llms.txt file.
- The
Placebo Protocol test (two identical sites) found no significant
citation difference between having llms.txt and not having it.
- Much
of the belief in llms.txt comes from confirmation bias, not
measurable cause and effect.
- Content
clarity and real authority matter far more than any single
text file.
FAQ
What is llms.txt used for? It's a text file
meant to guide AI models on how to interpret a website's content, similar in
concept to robots.txt.
Does llms.txt actually improve AI
visibility?
Current testing, including this experiment, shows no consistent, measurable
improvement for most sites.
What is GEO (Generative Engine
Optimization)?
GEO refers to strategies aimed at getting content cited or featured by AI
answer engines like ChatGPT, Gemini, and Perplexity.
Is llms.txt the same as robots.txt? No. Robots.txt
controls search engine crawling behavior and has a long, proven track record.
llms.txt is newer and its effectiveness is still unproven.
Should small businesses bother creating
an llms.txt file?
It likely won't hurt, but it shouldn't be treated as a priority. Focus on clear
content and real authority first.
Curious if your own llms.txt file is
actually doing anything? Try the same twin-site test yourself — and see what
the data really says.