We have run SEO audits using every tool on this list across dozens of client websites ranging from 50-page local businesses to 10,000-page ecommerce stores. The results vary more than you might expect. One tool might flag 2,000 issues on a site where another finds 300. The difference is not that one is more thorough -- it is that tools define and categorize issues differently. Understanding how each tool approaches auditing helps you interpret results correctly and avoid wasting time on low-impact fixes.

The free vs paid distinction matters less than you might think. Free tools can identify the same core issues as paid tools for sites under 500 pages. Where paid tools justify their cost is in scale (crawling thousands of pages), automation (scheduled recurring audits), and depth (connecting audit data to keyword and backlink insights). This comparison will help you decide whether you need those capabilities or whether free tools cover your situation.

What a Good SEO Audit Tool Should Check

A complete SEO audit needs to evaluate five distinct areas. Not every tool covers all five, which is why many professionals combine tools rather than relying on a single platform.

Technical health includes crawlability (can search engines find your pages), indexability (are the right pages being indexed), site speed (do pages load quickly enough), mobile friendliness (does the mobile version work properly), and security (is HTTPS properly configured). This is the foundation that every other optimization depends on.

On-page optimization covers title tags, meta descriptions, heading structure, keyword usage, internal linking, image optimization, and content quality. These are the factors you control directly on each page.

Content quality evaluates thin content (pages with too little value), duplicate content (internal and external), content freshness, and topic coverage gaps. AI search has made content quality evaluation even more critical because AI-generated results prefer comprehensive, well-structured content.

Backlink profile analyzes your link portfolio: total referring domains, link quality distribution, anchor text patterns, toxic links that could trigger penalties, and link velocity trends. Not all audit tools include this.

AI readiness is the newest audit category, evaluating how well your content is structured for AI-generated search results. This includes structured data quality, content clarity, factual accuracy signals, and source authority indicators. Currently, AIO Copilot's AIO Readiness Checker is the only tool that specifically evaluates this dimension.

Our Scoring Criteria

We scored each tool across six dimensions on a 10-point scale. These scores reflect our hands-on experience running audits with each tool, not marketing claims or feature lists.

Issue detection (weight: 25%): How many genuine, impactful issues does the tool identify? We penalized tools that inflate issue counts with trivial warnings and rewarded tools that focus on problems that actually affect rankings.

Actionability (weight: 25%): After running the audit, do you know exactly what to fix and how? Clear explanations, prioritized recommendations, and specific fix instructions score highest.

Coverage breadth (weight: 20%): How many of the five audit areas does the tool cover? Tools that handle technical, on-page, content, backlinks, and AI readiness score highest.

Ease of use (weight: 15%): Can someone without deep technical SEO knowledge run the audit and understand the results? This matters because most teams do not have a dedicated SEO specialist.

Value for money (weight: 15%): What do you get relative to what you pay? Free tools with strong capabilities score well. Expensive tools that offer minimal advantages over cheaper alternatives score poorly.

Free SEO Audit Tools

1. AIO Copilot Free Audit Tools

AIO Copilot's suite of 25 free tools provides the broadest coverage of any free audit option. The SEO Score Calculator evaluates overall SEO health with a numerical score and specific improvement recommendations. The Core Web Vitals Calculator measures performance against Google's thresholds. The Schema Markup Generator creates valid structured data. And the AIO Readiness Checker evaluates AI search readiness -- a category no other free tool addresses.

Strengths: Broadest feature coverage of any free option. No signup or account required. Includes AI readiness evaluation. Professional consulting available when you need expert interpretation. The combination of free tools and optional professional audit services covers the full spectrum of needs.

Limitations: Analyzes pages individually rather than crawling an entire site. Does not include backlink analysis. Best used alongside a crawling tool like Screaming Frog for comprehensive site-wide auditing.

Our score: Issue detection 8/10, Actionability 9/10, Coverage 8/10, Ease of use 10/10, Value 10/10. Overall: 8.9/10.

2. Screaming Frog Free Version

Screaming Frog's free version crawls up to 500 URLs and produces the most detailed technical crawl data available at any price point. It identifies broken links, redirect chains, duplicate titles and descriptions, missing H1 tags, oversized images, and dozens of other technical issues. The data export options let you create custom reports. For technical crawling specifically, nothing free comes close.

Strengths: Most thorough technical crawling available. Runs locally for data privacy. Highly configurable for advanced users. The level of technical detail per URL exceeds most paid cloud tools.

Limitations: 500 URL crawl limit excludes medium to large sites. No on-page content optimization analysis. No AI readiness evaluation. Steep learning curve for non-technical users. Desktop application requires installation. No scheduled or automated auditing in free version.

Our score: Issue detection 9/10, Actionability 6/10, Coverage 6/10, Ease of use 5/10, Value 9/10. Overall: 7.2/10.

3. SEOptimer Free Audit

SEOptimer provides a quick one-page SEO audit that covers the basics: performance, SEO fundamentals, usability, social signals, and security. Enter a URL and get a letter grade with explanations of each issue. The free version runs one page at a time and provides a reasonable overview for small business owners who want a quick health check without learning complex tools.

Strengths: Fastest way to get a basic SEO health check. Clean, easy-to-understand reports. No technical knowledge required. Includes social media presence evaluation. The white-label report feature (paid) is popular with agencies for client-facing deliverables.

Limitations: Free version is very limited -- one page analysis with basic metrics. Does not crawl multiple pages. Does not evaluate content quality in depth. The SEO checks are surface-level compared to dedicated tools. No backlink analysis in the free tier.

Our score: Issue detection 5/10, Actionability 7/10, Coverage 4/10, Ease of use 10/10, Value 6/10. Overall: 6.1/10.

Paid SEO Audit Tools

4. Semrush Site Audit

Semrush Site Audit is the most comprehensive cloud-based auditing tool available. It crawls up to 100,000 pages on the Pro plan and checks over 140 technical and on-page issues. The issue categorization separates errors (critical), warnings (important), and notices (nice to have), which makes prioritization straightforward. The thematic reports group related issues together, so you can tackle problems systematically rather than jumping between unrelated fixes.

Strengths: Most issues checked (140+). Clear prioritization with error, warning, and notice categories. Scheduled recurring audits track progress over time. Integration with Semrush's keyword and backlink tools connects audit findings to ranking impact. The comparability between audits shows whether your fixes are working.

Limitations: Requires a Semrush subscription starting at $139.95/month, and Site Audit is just one feature of the platform. The sheer number of issues flagged can be overwhelming without experience. Some flagged issues have minimal ranking impact. Does not evaluate AI search readiness. For a detailed platform comparison, see our Semrush alternative analysis.

Pricing: Included with Semrush Pro at $139.95/month (100K pages per audit), Guru at $249.95/month (300K pages), Business at $499.95/month (1M pages).

Our score: Issue detection 10/10, Actionability 8/10, Coverage 8/10, Ease of use 7/10, Value 6/10. Overall: 8.1/10.

5. Ahrefs Site Audit

Ahrefs Site Audit crawls your site and organizes issues into a health score with detailed breakdowns by category. The crawl is fast -- significantly faster than Semrush for large sites -- and the data is presented with Ahrefs' characteristic precision. The audit integrates with Ahrefs' backlink and keyword data, so you can see which pages with technical issues also have strong backlink profiles (making those fixes higher priority).

Strengths: Fast crawling even for large sites. Clean data presentation. Direct connection to backlink and keyword data helps prioritize which pages to fix first. The JavaScript rendering capability catches issues that simpler crawlers miss. Scheduled audits with email alerts for new issues.

Limitations: Fewer issue categories than Semrush (about 100 vs 140+). Issue descriptions assume more technical knowledge. The Lite plan limits crawl credits. Does not evaluate AI search readiness. For a comparison with other options, see our Ahrefs alternative analysis.

Pricing: Included with Ahrefs Lite at $129/month (10K crawl credits), Standard at $249/month (500K credits), Advanced at $449/month (1.5M credits).

Our score: Issue detection 9/10, Actionability 7/10, Coverage 8/10, Ease of use 7/10, Value 6/10. Overall: 7.7/10.

6. Sitebulb

Sitebulb is a desktop-based crawler that has built its reputation on making audit data understandable. Where Screaming Frog gives you raw data in spreadsheet format, Sitebulb provides visual reports with prioritized hints, context explanations, and even suggests which fixes to tackle first based on potential impact. The visualization of internal linking structure is the best available, showing orphan pages, link equity distribution, and crawl depth issues in intuitive diagrams.

Strengths: Best issue prioritization and explanation of any audit tool. Excellent visual reports that non-technical stakeholders can understand. Internal link visualization is unmatched. Runs locally for data privacy. The "hints" system explains not just what is wrong but why it matters and how to fix it.

Limitations: Desktop application requires local processing power for large crawls. No cloud version for remote teams sharing data. No built-in keyword or backlink analysis. Does not evaluate AI search readiness. Smaller community and fewer integrations than Screaming Frog.

Pricing: Lite at $13.50/month (10K URLs per crawl), Pro at $35/month (unlimited URLs). Annual billing saves approximately 20 percent.

Our score: Issue detection 9/10, Actionability 10/10, Coverage 7/10, Ease of use 9/10, Value 8/10. Overall: 8.6/10.

7. Woorank

Woorank provides an accessible website review that covers SEO, mobile, usability, social, and security. It presents results as a visual scorecard that is easy for clients and stakeholders to understand. The tool tracks your review score over time so you can demonstrate improvement. For agencies that need client-facing reports that look professional without requiring technical translation, Woorank fills a specific niche.

Strengths: Most visually polished reports. Excellent for client-facing deliverables. Tracks score changes over time. Covers a broad range of factors including social presence and local SEO. The competitor comparison feature shows how you stack up against specific rivals.

Limitations: Technical depth is limited compared to Screaming Frog or Semrush. Does not crawl beyond the analyzed page in the basic review. Issue counts are lower because it aggregates rather than listing individual instances. Pricing is high relative to the depth of analysis provided. Does not evaluate AI search readiness.

Pricing: Pro at $89.99/month, Premium at $199.99/month, Enterprise custom pricing.

Our score: Issue detection 6/10, Actionability 8/10, Coverage 6/10, Ease of use 9/10, Value 5/10. Overall: 6.6/10.

Complete Feature Comparison

Which SEO Audit Tool Should You Choose?

Best for Small Business Owners

Start with AIO Copilot's free tools for on-page and AI readiness analysis, plus Google Search Console for indexing data and Screaming Frog free for a site-wide crawl. This combination costs nothing and covers the issues that matter most. If you want a professional to interpret the data and create an action plan, our free SEO audit gives you expert analysis without commitment.

Best for Freelancers and Small Agencies

Sitebulb offers the best combination of depth and usability at its price point. The visual reports and prioritized hints save hours of manual analysis and produce deliverables that clients can understand. Supplement with AIO Copilot's free tools for on-page optimization scoring and AI readiness checks that Sitebulb does not cover. Total cost: approximately $35 per month.

Best for Enterprise and Large Agencies

Semrush Site Audit provides the most comprehensive cloud-based auditing with the best integration into keyword and backlink workflows. The ability to audit hundreds of thousands of pages on a schedule, track progress over time, and share data across team members makes it the right choice for large operations. Add AIO Copilot's free tools for AI readiness evaluation that Semrush does not yet provide.

Best for AI Search Preparation

AIO Copilot is the only option that evaluates AI search readiness. As Google AI Overviews expand and AI-powered search becomes the norm, this dimension of auditing will become essential. Every other tool on this list focuses exclusively on traditional ranking factors. Start with the free AIO Readiness Checker and scale to consulting when you need strategic guidance on optimizing for AI search.

Best Value Overall

The combination of AIO Copilot (free), Screaming Frog free version, and Google Search Console delivers 80 percent of the audit coverage that $140/month platforms provide. This stack handles on-page optimization, technical crawling, performance measurement, schema validation, AI readiness, and indexing monitoring -- all at zero cost. The remaining 20 percent (scheduled audits, backlink analysis, and large-scale crawling) only matters once your site or client portfolio outgrows the free tier limitations.

Frequently Asked Questions