An SEO audit is a health check for a website. It looks for anything that stops search engines from finding, understanding and trusting your pages, or stops visitors from becoming customers once they arrive. The result is a list of issues, ideally ranked by how much each one matters and how to fix it.
What a good audit covers
Crawlability and indexing. Can search engines reach and index your pages? Robots.txt rules, noindex tags, broken pages, redirects, canonical tags, sitemaps (see crawling).
On-page basics. Titles, meta descriptions, headings, image alt text, duplicate and thin content (see on-page SEO).
Links. Broken internal and outbound links, orphan pages, links pointing at redirects, and how the site links its important pages.
Speed and Core Web Vitals. Server response time, page weight, LCP and CLS (see Core Web Vitals).
Security. HTTPS, certificates, mixed content, security headers.
Structured data. Missing or invalid schema.
Mobile usability. Viewport, text size, tap targets, horizontal scrolling.
AI readiness. Whether AI crawlers can access the site, whether content depends on JavaScript, and whether an llms.txt file exists.
Trust and conversion. Contact details, author information, trust pages, clear calls to action.
Why it matters
Small technical problems hide easily. Coastline Plumbing’s audit finds that the “Discourage search engines” box was ticked on its staging site and copied to live during a theme update, adding noindex to every page. It also finds 14 broken links to a deleted service page and phone numbers that aren’t tappable on mobile. None of these was visible from the homepage, and the first one was costing nearly all its search traffic.
Prioritizing what to fix
An audit with 300 issues is only useful if you know where to start:
- Critical blockers: anything stopping pages being crawled or indexed, server errors, broken key pages.
- Revenue pages: issues on the service, product and contact pages that bring in customers.
- Site-wide patterns: a template problem fixed once fixes hundreds of pages.
- Everything else, in batches.
How often to audit
Run a full audit at least quarterly, and always after a redesign, migration, CMS change or major plugin update. Ongoing automated checks catch problems between full audits.
Common mistakes
- Treating the audit score as the goal instead of the fixes
- Fixing low-impact notices first because they’re easy
- Running an audit and never re-checking after fixes
- Ignoring technical SEO because “the content is good”
Tools
RankThat’s Site Audit runs 100+ checks across all of these areas and crawls as RankThatBot. Every issue comes with a plain-English “why it matters” and “how to fix”, and on WordPress many fixes can be drafted and applied through the Bridge plugin, then re-checked on the live site. For a quick one-page look, the free Website SEO Checker gives an instant summary.