Best Free LLM Audit Tools for AI Search Visibility

Our recommendation: Start with Big Fin’s free AI visibility score to establish an initial readiness baseline. Use a brand visibility checker to investigate mentions, then use Google’s tools to check the technical foundation.

By Michael Fleischner, founder of Big Fin SEO. Tool information reviewed October 29, 2026. This guide is published by Big Fin SEO, which operates the Big Fin GEO Assessment. Recommendations reflect use cases, not a scored head-to-head product test. Free access and features may change.

What are free LLM audit tools?

Free LLM audit tools help businesses investigate how they appear in AI search or whether their websites provide a sound foundation for discovery. LLM stands for large language model, the technology behind many AI assistants.

In marketing, an “LLM audit” usually refers to an AI visibility or generative engine optimization (GEO) assessment. It does not mean a security or performance audit of the underlying AI model.

The useful question is simple: when a potential customer asks for help finding a business like yours, does your business enter the conversation?

Answering that takes more than one score. You need to understand what AI systems say about your business, which sources they reference, and whether your website clearly explains what you do.

1. Big Fin GEO Assessment: start with your website’s AI readiness

Big Fin’s GEO Assessment offers a free AI visibility score based on your website and business details. The entry form requests your website URL, business name, location, and email.

Best fit: Business owners and marketers who want an initial assessment before deciding where to invest in GEO.

Free versus paid: The initial score is free. The full assessment report, including more detailed findings and recommendations, is a paid upgrade. Check the landing page for current pricing.

Treat the score as a diagnostic starting point. It is a proprietary assessment, not a published ranking from an AI platform or proof that your business appears in a specific percentage of answers.

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2. Ahrefs AI Visibility Checker: investigate brand mentions

Ahrefs offers a free visibility preview covering platforms including ChatGPT, Gemini, Perplexity, Copilot, and Google’s AI search features. Its checker provides a limited view of mentions, topics, and cited domains or pages.

Best fit: Marketers looking for an additional view of where a brand appears in the tool’s tracked data.

The free checker requires no signup. The preview shows limited results, while fuller data and historical tracking sit within the paid Brand Radar product.

For a smaller or local business, missing results should lead to more investigation. A tool’s coverage is not the same thing as every question your customers might ask.

3. HubSpot AI Search Grader: review brand perception

HubSpot describes its free AI Search Grader as a snapshot of how ChatGPT, Perplexity, and Gemini represent a brand. It covers areas such as sentiment, recognition, share of voice, and competitive positioning.

Best fit: Marketing teams investigating whether AI descriptions align with their positioning.

Review the substance of the answers as well as the score. Are your services described accurately? Is your business associated with the right category? Are important differences missing? A one-time assessment can help frame those questions, while ongoing monitoring is a separate need.

4. Google Search Console: check the discovery foundation

Google Search Console helps verified site owners investigate indexing, inspect URLs, submit sitemaps, and review Google Search performance.

Best fit: Businesses that need to understand whether important pages can be found and indexed by Google.

This is a supporting technical tool, rather than a cross-platform LLM visibility checker. Use it to investigate excluded service pages, unexpected canonical URLs, or search traffic changes.

Google states that a page must be indexed and eligible to appear with a snippet to qualify as a supporting link in AI Overviews or AI Mode. That makes indexability a practical place to start.

5. Google Rich Results Test: check structured data implementation

Google’s Rich Results Test checks a public URL or code snippet for structured data associated with supported Google search features.

Best fit: Website owners and developers checking the implementation of eligible structured data.

Use it after adding or changing markup. Correct errors, and make sure the marked-up information is also present on the page.

A passing result does not guarantee a special search appearance or an AI citation. For broader Schema.org syntax checks, use the Schema Markup Validator as a complementary check.

How to run a useful free AI visibility audit

1. Choose a business goal. Pick one service and market that matter to revenue, such as commercial HVAC maintenance in your service area.
2. Get an initial assessment. Run the free Big Fin score and record the date. Keep proprietary readiness scores separate from observed mentions.
3. Check customer questions. Try five to ten realistic, unbranded prompts in the AI platforms your customers use. For example: “What should I look for in a commercial HVAC maintenance provider in [city]?” Record whether your business appears.
4. Review citations. Save the actual source links. A mention of your company and a link to your website are separate outcomes.
5. Investigate priority pages. Use Search Console and structured data testing to identify technical issues on pages relevant to those questions.
6. Make a short action plan. Prioritize issues that prevent discovery, inaccurate business information, and missing answers to important buying questions.

Keep the measurements easy to understand

For a manual sample, calculate brand mention rate as answers naming your business divided by answers reviewed. Calculate website citation rate as answers linking to your domain divided by answers reviewed.

For example, if your business appears in three of ten answers and your domain is linked in one, your sample mention rate is 30% and your sample website citation rate is 10%. Those numbers describe that sample only. Keep prompts, platform settings, location, and timing as consistent as possible when comparing checks.

What should you fix after an LLM audit?

Turn findings into changes that help a customer understand and evaluate your business:

• Clarify your service pages. Explain who the service is for, where you provide it, what is included, and what happens next.
• Answer buying questions directly. Cover pricing factors, timelines, comparisons, limitations, and common objections with specific information.
• Show verifiable expertise. Add accurate author information, relevant experience, documented examples, and original evidence you can support.
• Keep business details consistent. Review your website, business profiles, and relevant directories for conflicting names, locations, or service descriptions.
• Fix discovery problems. Review indexing restrictions, internal links, canonical tags, and important content that is difficult to access.
• Use accurate structured data. Mark up facts that visitors can see. Avoid invented reviews, ratings, or unsupported claims.

For more context, read The Future of SEO in the Age of AI or explore Big Fin’s AI optimization services.

Which free LLM audit tool should you use first?

Our recommendation for a business owner is to begin with a clear baseline, then investigate the gaps. A score is useful when it helps you decide what to review next.

Start with Big Fin’s free score, compare what brand visibility tools report, and check the pages that support your most valuable services. Build your action plan around evidence from those checks.

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Frequently asked questions

What is an LLM audit tool?

An LLM audit tool evaluates part of your visibility or readiness for AI search. Some tools check whether AI answers mention your brand. Others assess website signals, indexing, or structured data. These are different measurements and should be reviewed together.

What is the best free LLM audit tool for a small business?

For a business owner who wants an initial website-focused assessment, Big Fin’s free AI visibility score is a practical starting point. Add Ahrefs or HubSpot for a separate view of brand visibility, then use Google Search Console to investigate indexing issues.

Is the Big Fin GEO tool completely free?

Big Fin offers a free AI visibility score. The full GEO assessment report is a paid upgrade. Review the current offer on the tool’s website before purchasing.

What is the difference between a brand mention and a website citation?

A brand mention means an AI answer names your business. A website citation means the answer links to a page on your website as a source. An answer can mention your business while citing another website.

Can an audit guarantee that ChatGPT will recommend my business?

No. An audit can identify issues and opportunities, but it cannot guarantee recommendations, citations, rankings, or traffic. AI answers vary with the prompt, platform, location, available sources, and timing.

Do I need special schema or an llms.txt file to appear in Google AI results?

Google says there are no special schema requirements or additional machine-readable files needed for inclusion in its AI search features. Focus on accessible, indexable pages, helpful content, and structured data that matches the visible page.

How often should I check AI search visibility?

A monthly review is a reasonable starting schedule for a small business. Recheck after substantial website changes and repeat the same relevant prompts so you can compare results. Record the platform, date, sources, and business location.

About the author

Michael Fleischner is a marketing expert, author, speaker, and founder of Big Fin SEO. He helps businesses connect marketing strategy, SEO, and AI search visibility with practical steps their teams can implement.

Sources and review notes

This comparison uses public product descriptions and official documentation reviewed on October 29, 2026. It does not claim hands-on testing of every tool or independent verification of vendor scoring methods.

• Big Fin GEO Assessment: free score and paid report
• Ahrefs: free checker features and limits
• HubSpot: AI Search Grader
• Google: getting started with Search Console
• Google: AI features and your website
• Google: Rich Results Test