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JSON Schema Validator

DevFormat JSON Schema Validator is a free, browser-based tool that validate your LLM JSON output against a JSON Schema to prevent hallucinated formats. It runs entirely on your device with zero data transmission, making it safe for proprietary code and sensitive content.

🛡️ 100% Client-Side. Your data never leaves your browser.
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Preventing LLM Hallucinations with JSON Schema Validation

Why Schema Validation Matters

Large Language Models (LLMs) are excellent at generating JSON, but they aren't perfect. Hallucinations can lead to missing fields, incorrect data types, or entirely wrong structures. By validating LLM output against a strict JSON Schema, you can ensure your application receives predictable data every time.

Ensuring Data Integrity in AI Pipelines

Automatic validation is the first line of defense in AI engineering. Our local-first tool allows you to test your schemas and payloads instantly in your browser, ensuring your 'Structured Output' prompts or 'Function Calling' definitions are robust enough for production environments.

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How to use

How to use JSON Schema Validator

  1. 1

    Paste your JSON Schema in the left panel.

  2. 2

    Paste the JSON payload you want to validate in the right panel.

  3. 3

    The tool will instantly show if the payload matches the schema.

  4. 4

    Review specific error messages to fix any mismatches.

FAQ

Which JSON Schema versions are supported?
We support Draft 4, 6, 7, and 2019-09 through the Ajv library.
Is my data sent to a server?
No, all validation happens locally in your browser's RAM.

Preventing LLM Hallucinations with JSON Schema Validation

Why Schema Validation Matters

Large Language Models (LLMs) are excellent at generating JSON, but they aren't perfect. Hallucinations can lead to missing fields, incorrect data types, or entirely wrong structures. By validating LLM output against a strict JSON Schema, you can ensure your application receives predictable data every time.

Ensuring Data Integrity in AI Pipelines

Automatic validation is the first line of defense in AI engineering. Our local-first tool allows you to test your schemas and payloads instantly in your browser, ensuring your 'Structured Output' prompts or 'Function Calling' definitions are robust enough for production environments.