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Free llms.txt Validator

Use this llms.txt Validator free online to check structure, Markdown syntax, links and overall quality. Paste content, upload a file or validate a live /llms.txt URL.

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Input
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Analyze
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Review Report
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Fix & Export

Paste raw Markdown

Paste the contents of your llms.txt file to validate it.

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What Is a Free llms.txt Validator?

The llms.txt Validator is a free tool designed to check if your llms.txt file complies with the current unofficial community standard. It verifies the structural integrity, Markdown syntax, reachability of linked resources, and the overall quality and clarity of your file.

Use this llms.txt Validator free workflow before publishing a new AI context file or after editing an existing file generated by an llms.txt generator tool.

How the Validator Works

This tool separates official format requirements from quality recommendations. It parses your Markdown file, maps its structure to llms.txt components, and evaluates them against over 30 specific formatting, compatibility, and quality rules.

What the Validator Checks

The tool checks everything from high-level structural requirements (like a mandatory H1 heading) to granular details like spacing between link titles and descriptions, duplicate URLs, and proper list formatting.

llms.txt Format Requirements

According to the current proposal, the only strictly required element is a top-level H1 heading containing the project or site name. Elements like blockquote summaries, introductory paragraphs, sub-categorizations, and link descriptions are optional but highly recommended.

Errors vs Warnings vs Suggestions

Errors represent structural issues where the content cannot be reliably interpreted. Warnings indicate issues like duplicate URLs or empty sections that reduce compatibility. Suggestions are optional improvements for clarity, such as replacing generic link titles.

How Markdown Validation Works

The tool builds an abstract syntax tree to identify headings, lists, links, and code blocks. It ensures your Markdown isn't broken, checking for unclosed tags, malformed links, or improper nesting that could confuse an AI parser.

How Link Checking Works

While full HTTP-status checking is best handled by the Link Checker, the Validator performs static analysis on links to detect malformed URLs, empty href attributes, and duplicate destinations.

How to Fix Common llms.txt Errors

The "Fix & Export" step provides one-click safe fixes for many common issues, like trimming trailing whitespace or removing duplicate links. For structural errors, you can use the inline editor to correct the Markdown manually.

What the Optional Section Means

Resources listed under an H2 section named exactly "Optional" are flagged as secondary. Compatible processors may omit these resources when producing shorter context, helping them focus on your primary documentation.

How to Validate a Live llms.txt File

You can easily validate a live file by entering its URL into the tool. The Validator will fetch the file and run the exact same comprehensive analysis as it would on pasted text.

Validator vs Formatter

The Validator provides a detailed report on the compliance and quality of your file. The Formatter is designed to automatically correct syntax and spacing issues without altering content, acting as a perfect companion tool.

Related Components

llms.txt Generator & Builder Create an llms.txt file manually, from a sitemap or from a list of URLs. llms.txt Formatter Clean, beautify and reorder sections. llms.txt Converter Convert between CSV, JSON and HTML. llms.txt Link Checker Find broken and duplicate URLs. llms.txt Analyzer & Previewer Preview, URLs, sections and word count. llms.txt Merge & Compare Tool Merge tool and diff checker.

Questions you might have

Is an H1 required?
Yes. It is the only required structural element in the current proposal.
Is the summary required?
No. It is optional but useful for explaining the site or project.
Are descriptions required after every link?
No. They are optional, but brief informative descriptions are recommended.
Can an llms.txt file contain external links?
Yes. External resources can be included when they help explain or support the project.
Is llms.txt mandatory?
No. Chrome currently describes it as an emerging and optional convention.
What does Optional mean?
Resources in the ## Optional section can be omitted by compatible processors when a shorter context is needed.
Does a valid file guarantee AI systems will use it?
No. Structural validity means the file follows the proposed format. Support and use depend on individual AI tools and crawlers.
Is llms.txt a replacement for robots.txt or sitemap.xml?
No. The proposal is designed to coexist with them and serves a different purpose.
llms.txt Generator & Builder Create an llms.txt file manually, from a sitemap or from a list of URLs. llms.txt Formatter Clean, beautify and reorder sections.