Auditing tool
SEO Audit Engine
Scores a website on what is actually holding it back in search.
What this build does
Most audit tools hand back a list of error codes and leave the owner to work out which of them matters. This one scores a website on 71 separate checks across 15 categories, from speed and structure through to reviews and the Google Business Profile, and returns one number, a band, and the findings in the order they are worth fixing. It runs behind the free audit on this site, and behind the lead engine that ranks businesses by what they are missing.
What it is for
One engine, used by everything that needs to know how a business looks online. The free audit on this site runs on it, the lead engine uses it to rank which businesses have the most to gain, and a build starts from it so the work begins with what is measurably wrong rather than with an opinion. Scoring logic lives in one place and every project reads from it, so the same site scored twice by two different tools gives the same answer.
What it runs on
TypeScript
Node.js
PostgreSQLLighthousePlaywrightPageSpeed InsightsDataForSEOFirecrawl
GitHubWhat we built
What it looks at
- Fifteen categories: the technical layer, whether search engines can crawl it, whether AI assistants are allowed to read it, titles and descriptions, structured data, visibility in search and on Maps, the Google Business Profile, the content itself, reviews, images and accessibility, whether there is any way to enquire, the legal pages, and whether anything is being measured at all.
- Only what can be seen from outside is scored. Anything needing the owner's login is left out rather than guessed at, which means every finding is something they can check for themselves.
- Each check carries a tier: 17 are core, 33 are high, and 21 are enhancements that lift a good site rather than rescue a poor one.
How the score is worked out
- A category scores as the weighted checks it passes over the weighted checks that apply to it, so a site is never marked down for something that was never relevant to it.
- The overall figure blends the categories by weight, and lands in one of three bands: under 40 is Poor, 40 to 75 is Fair, and 76 and above is Strong.
- 76 is not a round number picked for the look of it. It is the maximum margin boundary on the labelled data, chosen so every site sits at least a point clear of the line and a small change between runs cannot flip a business from one band to another.
- Anything the engine is less sure about surfaces as an opportunity rather than a penalty, so a site is never punished by a guess.
Making sure the score is right
- Calibrated against 30 hand-labelled sites, labelled by opening each one and judging it independently of the tool, and it now agrees with all 30.
- Getting there changed real things: a holding page that scored 48 is now capped, a transient failure that moved a site a whole band is retried, and the rules that spot a parked domain were tightened so a shop's coming soon tile no longer condemns a live site.
- Six independent agents were pointed at the engine to try to break the claims it makes, and everything they found was fixed.
- A Google rating is only attached to a business when that listing's own website address or phone number matches the site being scored, so a score can never borrow somebody else's reviews.
Built to be plugged into
- A versioned output contract, so a project that reads the engine today keeps working when the engine grows. New fields are added as optional within a version, and anything that would break a reader becomes the next version instead.
- Every data source sits behind its own adapter. If one is down its checks return not applicable and the completeness figure drops, rather than the whole audit failing.
- A batch mode for scoring a whole list: a free pass ranks everything, then the paid lookup is spent only on the top slice, and it stops at a budget set before the run starts.
- It runs as a service on its own server, so a project calls it rather than carrying a copy of it.
What it did
- Agrees with all 30 hand-labelled sites it is calibrated against, re-checked on 31 August 2026.
- 71 checks across 15 categories, from one URL and no login.
What comes next for SEO Audit Engine
- An interface other projects can call over the web, each with its own key, so a project that cannot import the code can still use the engine.
- A report as a PDF, themed per project, which is what turns the free audit on this site into something an owner keeps.
Run it on your own site
Put in your website address and it checks everything that can be seen from outside your site, from how fast your pages load on a phone to whether Google can read what you do. The full report lands in your inbox in a couple of minutes.
Ready when you are.
Written and kept up to date by Ben Criddle, who builds everything Fixr Systems ships.Last reviewed 2 September 2026