AI Fidelity Checker
AI ToolkitRuns entirely in your browser as a lexical heuristic, no AI model involved, no text sent anywhere.
How to use this AI fidelity checker
- Paste the original text on the left.
- Paste the AI's summary or rewrite on the right.
- Click "Check", names, numbers and dates not found in the original are highlighted for review.
What does this actually check?
This tool extracts "salient" terms from the AI output specifically, numbers, dates, percentages, and capitalized multi-word phrases that look like proper nouns, and checks whether each one appears anywhere in your original text. It's a lexical overlap check, not a semantic fact-checker: it flags terms that seem to have appeared from nowhere, which is a genuinely common signature of AI hallucination, without understanding whether the surrounding sentence is actually true.
Does this prove the AI output is wrong?
No, it flags specific names, numbers, and dates in the AI output that it couldn't find anywhere in your original text, as things worth double-checking. A flagged item might be a genuine error, a reasonable inference, or just phrased differently than in the source, it's a starting point for review, not a verdict.
Can this catch a subtly reworded fact that changes its meaning?
Not reliably, it checks whether specific terms appear in the source, not whether the overall meaning was preserved. A rewritten sentence that shifts meaning while reusing the same key terms won't be flagged.