Top Free Website SEO Checkers Compared

"SEO checker" is one of those phrases that's become almost meaningless through overuse. Type it into Google and you'll get everything from a full-site crawler to a single-page grader to a glorified word counter, all wearing the same label. I've watched clients paste a URL into three different "SEO checkers," get three wildly different scores, and conclude that SEO tools are basically astrology.

They're not — but the confusion is fair. Most "checkers" only look at one narrow slice of the picture and present it like a complete verdict. So let's actually separate what each type of checker does, so you know which one answers which question.

Crawlability checkers — "can a bot reach this page?"

This is the narrowest and most technical category, and it's usually the most important one to run first. The Crawlability Checker looks at robots.txt directives and meta robots tags for a given URL and tells you, plainly, whether search engines are allowed in. It won't tell you if your content is good. It will tell you if Google can even see it, which matters more.

Indexability checkers — "is it actually in the index?"

A page can be fully crawlable and still sit outside Google's index because of a stray noindex tag or a canonical pointing elsewhere. The Indexability Audit catches this specific, sneaky failure mode — one that a generic "SEO score" checker will usually miss entirely, because it's not looking at directives, just visible content.

On-page graders — the ones that give you a score out of 100

These are the most common type, and the most misleading if you don't know what's under the hood. Most "SEO score" tools are really just checking whether a title exists, whether a meta description exists, whether there's an H1 — presence, not quality. The HTML Tag Analyzer does this honestly: it shows you counts and content, and lets you judge quality yourself, instead of hiding the logic behind an opaque score that feels authoritative but isn't really measuring anything sophisticated.

Speed and mobile checkers

These test rendering performance, not content or crawlability. The Core Web Vitals Checklist and Mobile-Friendly Analyzer fall here. Worth noting: a page can pass every speed test and still be functionally invisible to Google if the crawlability layer is broken — speed and access are separate problems, and fixing one doesn't fix the other.

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Security checkers

Not technically an SEO factor in the classic sense, but HTTPS status affects trust signals and, indirectly, rankings. The SSL Certificate Checker tells you expiry dates and issuer info in one glance — worth running quarterly even if nobody asked you to.

The one thing no free checker replaces

Every tool in this list checks a mechanical signal — crawlability, tag presence, load time. None of them read your content and judge whether it actually answers the question a searcher had. That's still a human judgment call, and it's worth remembering before you treat any single "score" as the final word on whether a page is ready to publish.

Which checker for which question

Use this table as your decision tree next time you're not sure which tool actually answers your question.

Frequently Asked Questions

Why do different SEO checkers give different scores for the same page?

Because they're often measuring different things entirely, despite sharing the label "SEO checker." A crawlability tool and an on-page grader can both return a "score" while answering completely different questions.

Is a 100/100 SEO score a guarantee of good rankings?

No. Most scoring tools only check for the presence of elements, not their quality or relevance. A perfect technical score with weak content still won't rank well.

Which checker should I run first on a new site?

Crawlability, always. There's no point optimizing content or speed on a page search engines can't reach in the first place.