Quick answer
An unavailable llms.txt file means NOTABIS could not obtain a successful response from the optional /llms.txt resource. The finding is informational and does not indicate a Google indexing problem. Publish the file only if it supports a real documentation or AI-discovery purpose; otherwise, leave the optional resource absent.
What the issue means
llms.txt is an emerging proposal for a human-readable site summary. It is not robots.txt, a sitemap, a noindex directive, or a security boundary. A 404, 5xx, timeout, or other failed request means the resource was not available to this audit, but it says nothing about the accessibility of ordinary pages.
Why it matters for SEO
No major search engine requirement makes an llms.txt file necessary for crawling, indexing, or rankings. The file may be useful to a compatible AI or documentation consumer, but its absence should not drive SEO remediation or scoring. Keep public HTML, internal links, robots policy, and sitemaps healthy first.
How NOTABIS detects it
NOTABIS requests /llms.txt from the audited origin after it retrieves robots.txt. It records llms-txt-unavailable as an origin-level informational issue when the response status is 400 or higher or the request fails before a response can be recorded. The diagnostic stores the URL and, when available, status and content type. It does not judge whether the file is required or validate its contents.
How to check it yourself
Request the exact URL:
curl -sS -D - https://example.com/llms.txt -o /dev/null
Distinguish a deliberate 404 from a DNS, TLS, authentication, WAF, or timeout failure. Check whether a CDN or redirect serves an HTML challenge instead of text and inspect the final response from an external network.
How to fix it
If you want to publish the optional resource, create a concise plain-text file at /llms.txt, link only to public canonical pages, and return a successful response without a login gate. If you do not need it, document that choice and ignore the informational finding. Never expose credentials, private URLs, or unpublished customer data in an attempt to complete the check.
When this is intentional or does not need fixing
Leaving /llms.txt absent is a valid choice for most sites. Private, staging, and regulated systems may deliberately avoid publishing an AI-readable index. A temporary outage should be treated as a normal availability incident only when the file is part of a documented publishing workflow.
Related issues
Read llms.txt accessibility, robots.txt availability, and sitemap availability.
Run a NOTABIS audit
NOTABIS keeps an unavailable optional llms.txt result informational and shows the response evidence so you can decide whether any action is warranted.