Google Adds LLMs.txt to Docs After Publicly Dismissing It

Google has quietly uploaded an LLMs.txt file to its Search Central developer documentation portal, just months after the company's own Search Advocate, John Mueller, publicly dismissed the standard as ineffective.

Link to the LLMs.txt file: https://developers.google.com/search/docs/llms.txt 

The Discovery

The implementation was spotted by SEO professional Lidia Infante on December 3, 2025, who posted her discovery on Bluesky with a pointed question directed at Mueller: "Is this an endorsement of LLMs.txt or are you trolling us, John?"

Mueller's cryptic response, a simple "hmmn :-/"- has done little to clarify Google's position on the controversial web standard.

A History of Scepticism

The discovery is particularly surprising given Google's consistent dismissal of the LLMs.txt format throughout 2025. Mueller has repeatedly stated that no major AI system uses the standard, at one point comparing it to the outdated keywords meta tag, a feature abandoned by search engines years ago due to concerns about manipulation.

In June 2025, Mueller stated unequivocally: "No AI system currently uses llms.txt."

He emphasized that server logs clearly show AI bots aren't even checking for these files, making them essentially useless for website owners.

What is LLMs.txt?

Proposed in late 2024, LLMs.txt is a markdown file designed to help large language models access and understand website content more efficiently. Unlike robots.txt, which controls bot access, LLMs.txt aims to provide AI systems with a curated map to a site's most important content, stripping away ads, navigation, and other non-essential elements.

The Contradiction

Google's decision to implement LLMs.txt for its own developer documentation directly contradicts the company's public messaging. While Mueller has warned that the format could be abused for cloaking, showing different content to AI bots versus human visitors, Google has now chosen to use it for one of its most important technical resource hubs.

The move raises several questions:

• Is Google testing the standard internally before making any formal announcements?
• Does this signal a potential shift in the company's position on LLMs.txt?
• Or is this simply a case of different teams within Google operating independently?

What This Means

For now, Google's implementation of LLMs.txt appears to be an isolated case rather than a policy shift. The company has not issued any official statement endorsing the standard, and Mueller's ambiguous response suggests internal uncertainty about the decision.

However, the mere fact that Google has chosen to implement LLMs.txt for its own documentation could lend legitimacy to the format, regardless of the company's official stance.

Website owners watching this space should note that while Google has quietly adopted LLMs.txt for its own purposes, the company continues to maintain publicly that the standard offers no ranking benefits and isn't used by any major AI systems.

Whether this represents a genuine change in direction or simply internal experimentation remains to be seen. For now, the irony is not lost on the SEO community: Google has implemented the very standard its representatives have spent months dismissing.

What happens next will likely depend on whether Google chooses to address this contradiction or continues to let the mystery deepen with cryptic emoji responses.

The Plot Thickens

In yet another twist, the LLMs.txt file that Google quietly added to its developer documentation is no longer accessible. As of later the same day, the URL returns a 404 error, raising questions about whether Google removed the file deliberately or if this is simply a technical issue.

The disappearance of the file within hours of its discovery only adds to the confusion surrounding Google's stance on LLMs.txt, making the entire episode even more bizarre.