The other half

The checks a browser tab is not allowed to run

Every tool on this site works on input you paste. None of them can fetch your live URL and tell you what came back — and that is a rule of the web rather than a shortcoming of static hosting.

Why the split exists

A page served from visibility100x.github.io cannot fetchyourdomain.com and read the response. The same-origin policy forbids it, and browsers enforce it without exception unless the other origin explicitly opts in with CORS headers — which your site has no reason to do, and which most sites correctly do not.

This is a good rule. Without it, any page you opened could quietly read your logged-in webmail, your bank statement and your company intranet, and report what it found. So a "free browser-based site checker" that genuinely fetched arbitrary URLs would either be lying about where the fetch happens, or be a security hole. The honest options are to run the fetch on a server, or not to offer the check.

We run them on a server, on the main site, and they are free there. Below is what each one is for, so you can go straight to the one that answers your question instead of running a full audit to find out.

What AI can read

Whether an assistant fetching your page gets your content or an empty shell, and whether it was allowed to fetch it at all.

AI crawler checkerTells you which AI crawlers your robots rules currently let through. Roughly 28% of sites block at least one without anybody having decided to.visibility100x.com ↗JavaScript render gap checkerCompares the HTML served on the first response with what appears after scripts run. Most AI crawlers never run the scripts, so the first number is the one that counts.visibility100x.com ↗AI content readinessLooks at whether the page states its claims in liftable, self-contained sentences, which is what determines whether it gets quoted rather than skimmed.visibility100x.com ↗llms.txt checkerFetches the live path and reports whether a real file is served, which catches servers answering with a soft 200 and a copy of the homepage.visibility100x.com ↗Structured data checkerParses the JSON-LD on the page and reports what it actually claims, including the mismatches between markup and visible content that quietly invalidate it.visibility100x.com ↗

Crawling and indexing

The mechanical questions about whether a page can be found, fetched and kept.

robots.txt checkerReads the live file and resolves which rules apply to which agent, which is harder than it looks once a file has more than one user-agent block.visibility100x.com ↗XML sitemap checkerValidates the sitemap and checks that the URLs inside it are the canonical, indexable ones rather than redirects and dead ends.visibility100x.com ↗Indexability checkerResolves every signal that can keep a page out of the index — robots rules, meta robots, headers, canonicals — and reports the one that wins.visibility100x.com ↗Canonical tag checkerChecks the canonical resolves to a live page that agrees, which is where apex and www variants usually turn out to disagree.visibility100x.com ↗hreflang checkerVerifies the return links, because hreflang only works when both pages name each other and one-way declarations are ignored.visibility100x.com ↗Content freshness checkerReports the dates the page publishes and whether they agree with each other, which matters on queries where recency decides what gets cited.visibility100x.com ↗

On the page

The elements that decide how a page is summarised, in results and in answers.

Title tag checkerReads the title your live page actually serves, after the CMS and any plugin that rewrites it.visibility100x.com ↗Meta description checkerConfirms a description exists, is unique, and is not the boilerplate every page on the site shares.visibility100x.com ↗Heading structure checkerReports the heading outline as a machine reads it, which is how a model decides what the page is about before reading the prose.visibility100x.com ↗Image alt text checkerFinds images with missing or filename-shaped alt text, which is an accessibility failure first and an extraction failure second.visibility100x.com ↗Open Graph checkerChecks the card that renders when someone pastes your URL into a chat, which is often the first impression a link makes.visibility100x.com ↗

Speed and security

What a crawler experiences before it reads a word, and what a browser warns about.

Core Web Vitals checkerPulls the field and lab measurements together so a lab score that swings between runs is not mistaken for a real regression.visibility100x.com ↗Page speed checkerReports what makes the page slow rather than only how slow it is, which is the half of the answer you can act on.visibility100x.com ↗Security headers checkerChecks the response headers that decide whether a browser trusts the page, including the ones that break embeds when set carelessly.visibility100x.com ↗

If you would rather run one thing

The full AI visibility audit runs the whole set against a single URL and returns them as one report, which is the right starting point when you do not yet know which of the nineteen questions you have. The individual checkers above are better once you do.

For work that needs doing rather than listing, themanaged service is the paid side of that site. Everything on this one stays free and open source, and thefive browser tools here will never need an account.