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Schema Tool Checker

Check your Schema.org structured data quickly: paste JSON-LD (or an HTML snippet with <script type="application/ld+json">) and get a clean report with errors, warnings, node/type summary, and common JSON-LD gotchas. Runs fully offline in your browser.

Category: SEO · URL: /tools/schema-tool-checker.html
Tip: press Ctrl/⌘ + Enter to run Check. No network calls; everything stays in your browser.

      
Output is a compact report for “Check”, and the JSON string for “Format/Minify”.

    

  


  

    
Related tools

    
  



          

          

            Privacy: runs locally in your browser. No uploads, no tracking scripts.
          

        

      


      
    


    

      
How to use

      
Use it to sanity-check schema markup before you run deeper tests.
  1. Paste JSON-LD, or paste HTML that contains one or more application/ld+json script tags.
  2. Leave “Extract from HTML” on if you pasted HTML.
  3. Click Check (or press Ctrl/⌘ + Enter).
  4. Fix issues reported under Errors/Warnings, then re-check.
  5. Use Format or Minify for a clean final JSON-LD block.

      

        Keywords this page targets (natural cluster): schema tool checker, schema checker, json-ld schema checker, structured data checker offline, schema markup checker, json-ld validator, validate schema.org json-ld, check schema script tag, extract json-ld from html, schema @context checker, schema @type checker, schema @graph checker, duplicate @id schema, format json-ld, minify json-ld, schema markup linter, structured data debugging, schema validation tool
      

      

        Secondary intents covered: Validate that JSON-LD parses correctly (no broken JSON)., Extract JSON-LD from an HTML page snippet with script tags., Confirm @context and @type are present and in the right shape., Identify duplicate @id values inside @graph., List detected Schema.org types and node counts for a quick sanity check., Format (pretty-print) or minify JSON-LD before publishing., Spot common mistakes like context/type without the @ prefix., Copy the final output/report for sharing or tickets.
      

    


    

      
FAQ

    
What does this schema tool checker validate?
It checks JSON validity and flags common JSON-LD issues like missing/odd @context, missing/invalid @type, duplicate @id, empty strings, and basic URL-looking values.
Can I paste a full HTML page to check schema?
Yes—keep “Extract from HTML” enabled and paste HTML; it will pull content from <script type="application/ld+json"> blocks.
Does this replace Google’s Rich Results Test?
No. This is a fast offline sanity check; search engines apply their own rules and eligibility requirements.
Why do I see “Missing @context” if my schema is inside @graph?
@context is typically expected at the top level; if you’re using multiple blocks or unusual nesting, this tool warns so you can confirm your structure is intentional.
Can it format or minify my JSON-LD?
Yes—use “Format” for pretty JSON and “Minify” for compact output (single block only).
Is my data sent to a server?
No. The checker runs locally in your browser and doesn’t make network requests.
What should I do if JSON parsing fails?
Fix the JSON first (missing quotes, extra commas, unescaped characters). Once it parses, the checker can run the markup checks.


    


    
  


  ","expected":"Duplicate @id"},{"name":"Invalid JSON fails","input":"{\"@context\":\"https://schema.org\",}","expected":"JSON parse error"}];

    // The tool JS must attach:
    // - window.feutexReset(): resets UI
    // - window.feutexSelfTest(tests): returns string log (PASS/FAIL)
    // - window.feutexInit(): optional
    (function(){
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      const btn = document.getElementById('selfTestBtn');
      const resetBtn = document.getElementById('resetBtn');
      function setLog(txt){ if(log) log.textContent = txt || ''; }
      btn?.addEventListener('click', async () => {
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          if(typeof window.feutexSelfTest !== 'function') {
            setLog('Self-test missing: window.feutexSelfTest not defined.');
            return;
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          const out = await window.feutexSelfTest(FEUTEX_SELF_TESTS);
          setLog(out || 'No self-test output.');
        } catch(e) {
          setLog('Self-test error: ' + (e?.message || e));
        }
      });
      resetBtn?.addEventListener('click', () => {
        try {
          if(typeof window.feutexReset === 'function') window.feutexReset();
          setLog('');
        } catch(e) {
          setLog('Reset error: ' + (e?.message || e));
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      });
      try {
        if(typeof window.feutexInit === 'function') window.feutexInit();
      } catch(_e) {}
      document.getElementById('yr').textContent = String(new Date().getFullYear());
    })();
  

  

  ',
        expectIncludes: ['Duplicate @id', 'Blocks: 1']
      },
      {
        name: 'Invalid JSON fails',
        input: '{"@context":"https://schema.org",}',
        expectIncludes: ['JSON parse error']
      }
    ];

    let pass = 0;
    const logs = [];
    for(const t of tests){
      const out = internalCheck(t.input);
      const ok = t.expectIncludes.every(s => out.includes(s));
      logs.push((ok ? 'PASS' : 'FAIL') + ' - ' + t.name);
      if(!ok){
        logs.push('  Expected to include: ' + t.expectIncludes.join(' | '));
        logs.push('  Got: ' + String(out).slice(0, 240).replace(/\n/g, ' \\n '));
      } else {
        pass++;
      }
    }
    logs.push('Result: ' + pass + '/' + tests.length + ' passed');
    return logs.join('\n');
  };
})();