What is an SEO audit?
An SEO audit is a check of whether search engines can find your pages, understand them and choose to show them. A useful one ends with a short, ordered list of what to change first.
The quickest way to see what one finds on your own site is to run one. Check Engine runs 99 checks on your own computer, with no account and no sign-up:
Free: your score, how many problems in each category, and the top problem in full with its fix. Pro: the rest of the problems, the ranked fix plan and the markup to paste. For Macs with Apple silicon or Intel, macOS 12 or later, and 64-bit Windows. Intel Mac download, Windows and other downloads.
To check a single page first, with nothing to install, the free SEO checker scores one address in your browser and shows what to fix on it.
What does an SEO audit include?
Start with whether search engines can reach and index the pages. Then check what those pages say, how they load and how they link together. A good audit separates faults a tool can find from questions that need a person to read the page.
Crawlability and indexing: the gate
Can search engines reach the page, and are you telling them to index it? This is where the
site-killing mistakes live: a noindex left on after a redesign, a robots.txt
Disallow: / carried over from staging, canonicals pointing at another domain,
redirect loops. These faults can go unnoticed by the site owner while affecting how search
engines reach or index the pages.
Use the robots.txt tester to check whether a rule blocks a page. For an archive that points every canonical at its first page, check the pagination canonicals.
Two numbers from reading the robots.txt of the Tranco top 10,000. Of the 1,616 sites writing a rule aimed at an AI crawler, 838 (51.9%) name a user-agent token no crawler answers to, so the rule they wrote does nothing. And 643 of the 10,000 refused a self-identifying bot at the server before robots.txt was even consulted, which no amount of editing that file will fix. Both are measured here.
On-page
Titles, meta descriptions, heading structure, image alt text, internal anchor text. Mostly
straightforward, but two details matter more than people expect: search engines truncate titles
by pixel width rather than character count, and alt="" is the correct
markup for a decorative image, not a missing alt.
Content
Whether pages answer the question someone actually asked. Thin pages, unfinished template copy left in production, unedited AI-generated copy, missing author and date signals.
Speed
Time to first byte, page weight, render-blocking resources, layout shift risk. Note the limit: Core Web Vitals are field measurements and need a real browser under real conditions. Any tool claiming to measure your LCP from a static crawl is estimating.
Structured data
Schema.org markup that tells a search engine what the page is. Most real-world
business schema sits inside an @graph array, which naive validators miss entirely
and then report as absent.
We read the homepage JSON-LD of 85 well-known sites: 50 declare
an organisation and only 41 declare sameAs, the property that
links that organisation to anything else. 9 went to the
trouble of describing themselves and then connected it to nothing.
The dataset is here.
The three that most audits skip
- Local business signals: NAP consistency, LocalBusiness schema and its subtypes, opening hours, geo targeting. For a plumber or a restaurant this is organic search.
- AI search visibility: per-crawler access, server-side rendering, entity resolution. Explained here, and the directives themselves are on letting ChatGPT and Perplexity read your site.
- Conversion: whether the traffic you earn has anywhere to go. The most expensive failure on any site is a page that ranks and converts nobody: nine checks that apply to a landing page rather than to a crawl, and whether your tracking is on every page, which is a different question from whether it is installed.
What audits of 14 small-business sites found (2 November 2026)
On 2 November 2026 we ran Check Engine against 14 small-business sites (a dental practice, a plumber, an electrician, a family-law firm and others), using the app's default scope (200 pages, growing to at most 1,000 while a larger site answers quickly), with the network checks off. Each site is named here only by what kind of business it is. The median site scored about 74 out of 100 and had 42 or 43 problems; the problem counts ran from 20 to 63. Of the 14, 6 graded D, 2 C, 5 B and 1 A.
The most common area was On-page SEO: a median of 9 problems a site. Next came Crawlability & indexing, at 5.5. Crawlability, the gate described above, had problems on 12 of the 14 sites. In 6 of the 13 areas, all 14 sites had at least one finding. A clean audit is rare. What an audit is for is the order: which of those problems to fix first.
| Area | Median problems | Sites with any |
|---|---|---|
| On-page SEO | 9 | 14 of 14 |
| Crawlability & indexing | 5.5 | 12 of 14 |
| Content quality | 4.5 | 14 of 14 |
| AI search visibility | 3.5 | 14 of 14 |
| Speed & Core Web Vitals | 3 | 13 of 14 |
| Tracking & campaign readiness | 3 | 14 of 14 |
How can I run a free SEO audit?
Start with a page you need people to find. Check its crawl access, title, headings and canonical, then look for the same faults across the site. Fix access problems before polishing copy that search engines cannot read. The free SEO audit tools list shows which tools check a page, which crawl a site and where their free versions stop.
How often should I run an SEO audit?
Quarterly is right for most sites, with lighter monitoring between. Run one immediately after a redesign, a migration, a CMS change, or an unexplained traffic drop: those are when the fatal, invisible mistakes get introduced.
How often you can run one also depends on how the tool is paid for. If you already pay for Ahrefs, its crawler is Ahrefs Site Audit; our comparison sets out what it checks and how a crawl is paid for.
What a good audit report looks like
Three tests. If a report fails them, it will not get acted on:
- Is there a first task? Not a category: a specific first thing.
- Does every finding say what it costs you? "Missing meta description" is a fact. "Google is writing your search snippet from a cookie notice" is a reason.
- Does it admit what it could not check? A report with no gaps either checked nothing or is hiding something. If a crawl was blocked or only reached part of a site, that has to be on the page.
Check Engine is built around those three. It runs 99 checks on your own computer, ranks everything by impact against effort, and marks areas it could not assess as unknown rather than passing.
Common questions
What is an SEO audit?
An SEO audit checks whether search engines can find your pages, understand them and choose to show them. Its useful result is an ordered list of fixes, with the affected pages and what to change.
Can I do an SEO audit for free?
Yes. Start with a free page check, then use a site crawl to find faults between pages. Check Engine's free download shows your score, problem counts by category and the top problem in full with its fix. The rest of the problems and ranked plan are paid.
What does an SEO audit include?
Crawlability and indexing, on-page markup, content quality, speed, structured data, local business signals, AI search visibility and conversion.
How often should I run an SEO audit?
Quarterly for most sites, with lighter monitoring in between. Run one immediately after a redesign, migration or unexplained traffic drop: those are when invisible, fatal mistakes get introduced.