Find out what AI engines actually see in your schema.
Paste a URL. Schema Sniffer reads the structured data on the page, finds the errors, the thin bits and the missed opportunities, and writes the whole thing up in plain English. About ten seconds, no signup, full report on screen.
Sniffing around...
- 0 errors
- 0 flaws
- 0 opportunities
The fix
Paste-ready JSON-LD for every missed opportunity above.
One page is the conversation starter. The whole site is the work.
If you want this done across every page on the site, with the schema written, tested and the rich-results gain measured, hit the button.
Three things, in about ten seconds.
No dashboard, no signup, no email until you ask for the snippets.
It picks up the scent
The tool fetches your page, pulls out every JSON-LD block, parses each one, and works out what kind of page it is looking at: homepage, article, product, service, contact, FAQ, case study, or something more bespoke.
It runs the rules
About twenty rules, grouped into errors (schema that is broken), flaws (schema that is present but thin) and opportunities (schema that should be there for that page type but is not). Every finding gets a severity and a stake.
It tells you the story
Claude Haiku 4.5 rewrites the findings in plain English, explaining what each one costs you with the AI engines that actually use structured data. Then it generates the snippets you would paste in to fix them.
Fair questions before you paste a URL.
What does Schema Sniffer actually check?
It fetches the URL you give it, extracts every JSON-LD block, parses each one, and runs it through about twenty rules covering errors, flaws and missed opportunities for the type of page it is looking at. The output is a score, a verdict, every finding written out in plain English, and paste-ready JSON-LD for the gaps.
Is it really free?
Yes, completely free. The full report shows up on screen with no email required. The only thing gated is the JSON-LD snippets that fix the missed opportunities, and that gate is one email field. You get the snippets on screen and a copy in your inbox.
Which AI engines does it think about?
The rules and the commentary are written for the engines that structured data actually feeds: ChatGPT, Claude, Gemini, Perplexity and Google's AI Overviews. It is not just a Rich Results validator with a fresh coat of paint. It is opinionated about what AI search wants.
Does it check microdata or RDFa too?
It detects them and flags their presence, but the rule engine focuses on JSON-LD because that is what every major AI engine reads most reliably. If you have microdata, migrating to JSON-LD is usually the recommendation anyway.
How many sniffs can I run?
Three per domain per day, twenty per IP per day. Enough to check the most important pages without burning the API bill it costs to keep this free.
Will it work on a JavaScript-rendered site?
If your structured data is rendered server-side or baked into the HTML at build time, yes. If your schema is injected by client-side JavaScript only, version one will miss it. That is increasingly rare and is on the list to address.