Free SEO Audit Tool — Crawl Your Whole Site, Fix Every Issue
Crawl your entire website and get back a prioritised list of every SEO problem holding it back — over 60 checks per page across technical, on-page, structure and content. Every crawl grades your SEO, accessibility and security in one pass, validates your structured data, and — uniquely — tells you whether AI search engines like ChatGPT and Perplexity can find, read and cite you. Free, and no desktop software to install.
One crawl, three grades
Most audit tools give you an SEO score and stop there. RankNibbler grades every page three ways in a single crawl:
- SEO score — a 0–100 score and an A–F grade, with a prioritised list of what's wrong and how to fix it.
- Accessibility — a WCAG / axe-style grade covering 22 common accessibility rules.
- Security — an A–F security-headers grade (HSTS, CSP, X-Frame-Options and more), plus mixed-content checks.
Crawl your whole site
Point it at your site and it crawls page by page — no 500-URL desktop cap, no software to install. You choose the scope:
- Crawl the whole website (following internal links), your XML sitemap, or a list of URLs you provide.
- Honour robots.txt (or supply your own rules, or ignore it for a full picture).
- Re-render JavaScript pages so client-side apps are audited on their real content, not an empty shell.
- Control depth, page limits, crawl speed and what's in scope (include/exclude rules, subdomains, start folders).
A prioritised issues report
Every finding from every page rolls up into one report, ranked by severity — high, medium and low — and grouped into technical, structure and content. You fix what matters first, with a recommendation and the list of affected pages for each issue. Across the crawl it runs more than 60 distinct checks, including all of the below.
Technical SEO checks
- Indexability & noindex — pages excluded by a meta robots or X-Robots-Tag, and a clear indexable / not-indexable verdict with the reason.
- Canonical tags — missing, non-self-referencing, or canonicalised-away pages.
- robots.txt & XML sitemaps — parsed and validated, including sitemap problems and URLs found only in the sitemap.
- Redirect chains, loops & broken redirects — multi-hop redirects, infinite loops, and redirects to dead URLs.
- Broken links — internal links pointing at 4xx/5xx pages.
- HTTPS & mixed content — non-HTTPS pages and secure pages loading insecure resources.
- Status codes, response time, page weight, compression and outdated doctypes, charset problems and error text in the source.
On-page SEO checks
- Title tags — missing, duplicate, too long (by pixel width, not just characters) or too short, and word repetition.
- Meta descriptions — missing, duplicate, too long or too short.
- Headings — missing or multiple H1s, duplicate H1s, skipped heading levels, and a title↔H1 mismatch check.
- Keyword coverage — title and H1 keywords that don't appear in the body, and pages not optimised for any clear term.
Duplicate content & cannibalisation
- Duplicate titles & meta descriptions across pages.
- Near-duplicate content — pages that are substantially the same (detected with content fingerprinting, so sort/filter URL variants don't false-flag).
- Keyword cannibalisation — pages competing for the same focus keyword.
- Duplicate text blocks reused across multiple pages (boilerplate excluded).
Site structure & internal links
- Orphan pages — pages with no internal links pointing to them — and pages with very few inlinks.
- Internal PageRank — which pages your own link structure favours, computed across the crawl.
- Anchor text — empty, generic ("click here"), over-long or identical competing anchors.
- Hreflang — non-reciprocated or misused alternate-language links.
Structured data validation
It extracts your JSON-LD, microdata, Open Graph and Twitter cards, and goes further than counting blocks: it validates the required and recommended fields for 18 schema.org types — Article, Product, LocalBusiness, Organization, FAQPage, BreadcrumbList, HowTo, Event, Recipe, Review, VideoObject, Person and more — flagging missing required fields as errors and missing recommended ones as warnings.
Content quality
- Thin & missing content — pages with too little text to rank.
- Readability — scored with six formulas (Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau, ARI) on real prose.
- Images — missing alt text (named, so you know which), missing dimensions (layout shift) and modern formats.
- Mobile — missing or zoom-blocked viewport, plus deprecated HTML, frames and Lorem Ipsum placeholder text.
Accessibility & security, graded
Because accessibility and security increasingly shape trust and rankings, every page is graded on both — not as an afterthought, but in the same crawl:
- Accessibility — 22 WCAG / axe-subset rules (image alt, form labels, link & button names, heading order, landmarks, valid ARIA, document language and more), each with an impact level.
- Security headers — an A–F grade weighting HSTS, Content-Security-Policy, X-Content-Type-Options, X-Frame-Options, Referrer-Policy and Permissions-Policy, with CSP weakness flags and mixed-content detection.
AI & agent readiness — the part nobody else checks
Search is no longer just Google. Increasingly, your visibility depends on whether AI search engines and assistants can crawl, read and cite your pages — and almost no audit tool checks it. RankNibbler does, in the same crawl:
- AI crawler access — whether your robots.txt allows or blocks the 15 named AI bots (GPTBot, OAI-SearchBot, ChatGPT-User, ClaudeBot, PerplexityBot, Google-Extended, Applebot-Extended, CCBot and more), mapped to the product each one feeds.
- llms.txt & agent-discovery standards — whether you publish a valid llms.txt and the emerging .well-known / agent-discovery signals.
- Per-page AI-citation signals — a direct-answer opening paragraph, question-led (Q&A) structure, statistics and authority citations, E-E-A-T signals (author, dates, organisation), and Speakable schema — the things that make a page quotable in an AI Overview.
- Raw vs rendered gap — content that's visible in a browser but missing from the HTML an AI crawler actually reads.
Built for real-world sites
A crawler is only useful if you can trust its findings. RankNibbler handles the awkward cases that make other tools cry wolf: it re-confirms bot-protected (Cloudflare-style) pages through a real browser, recovers pages that briefly rate-limit, and quarantines genuinely-blocked pages so they can't manufacture fake "missing title" or "duplicate" findings. So your report reflects your site, not the crawler getting blocked.
How to run a site audit
It's three steps:
1. Enter your site URL
Add your site and choose what to crawl — the whole website, your XML sitemap, or a list of URLs.
2. Let it crawl
RankNibbler crawls the pages, audits each one, and rolls every finding up into a prioritised issues report with your three grades.
3. Work the issues top-down
Fix the high-severity issues first, then medium and low, using the per-issue recommendation and the list of affected pages.
Frequently asked questions
What is an SEO audit?
A full review of the technical, on-page, structure and content factors affecting your search rankings, which flags the issues holding you back and how to fix them.
What's the difference between a site audit and an SEO audit?
A site audit is the full-site crawl; an SEO audit is the analysis of what that crawl finds. RankNibbler does both in one pass.
Is there a genuinely free SEO audit tool?
Yes — RankNibbler crawls your site and runs over 60 checks per page for free, with no paywall on the analysis. It's included with a free account.
How do I do an SEO audit?
Enter your URL, let the crawler scan every page, then work the prioritised high/medium/low issues list from the top down, fixing the high-severity items first.
What does a technical SEO audit check?
Crawlability, indexability and noindex, canonicals, robots.txt, XML sitemaps, redirect chains, broken links, structured data, and page timing and weight.
What is a good SEO score?
On RankNibbler's 0–100 scale, 80+ is healthy, 60–80 needs work, and under 60 signals issues that are actively hurting the page. Every page also gets an A–F grade.
How often should I run a site audit?
Quarterly as a baseline, monthly for active or large sites, and always after a redesign, migration or major content change.
Can AI assistants like ChatGPT and Perplexity find my site?
The AI-readiness check shows whether your robots.txt allows GPTBot, ClaudeBot, PerplexityBot and Google-Extended, whether you have an llms.txt, and scores each page's AI-citation signals.
What is llms.txt and do I need one?
It's a root file that guides AI crawlers to your key content. The audit checks whether you have a valid one and flags what's worth adding.
Does the audit also check accessibility and security?
Yes — every crawl returns a WCAG/axe accessibility grade and an HTTP security-headers grade alongside the SEO score, so you get three grades in one run.
Audit your site free
Run your first crawl in minutes — it's free, and it sits alongside the rest of your SEO tools.