JSON Schema Generator Validator Tool - Multi-Sample Schema Inference with Format Detection

First Published: 2026-04-02
Last Updated: 2026-04-02

Generate JSON Schema from one or multiple JSON samples, or validate JSON data against a schema. All processing is performed entirely in your browser - your data never leaves your device.

⚠️ IMPORTANT DISCLAIMER:

This tool is provided "AS IS" without any warranties of any kind.
The author accepts no responsibility for data loss or any issues arising from use of this tool.
Generated schemas should be reviewed and refined before production use.
The built-in validator covers common JSON Schema keywords but is not a fully certified implementation.
By using this tool, you accept full responsibility for any outcomes.

This tool uses client-side JavaScript for all processing. No data is transmitted to servers, no files are uploaded online, all processing happens locally in your browser. Once loaded, this tool continues to work even without an internet connection. For more details, please refer to our Web Tools Disclaimer.

JSON Sample 1:

Schema Options

Draft Version:

Detect formats (email, URI, date-time, UUID, IPv4, IPv6)

Suggest enums (multi-sample)

Enum max values:

Mark required fields

additionalProperties:

How to Use This JSON Schema Tool

Generate Schema

Paste JSON: Enter one or more JSON samples into the input areas
Add Samples: Click "Add Sample" to provide additional JSON objects. Properties present in some samples but not others are automatically marked as optional
Configure Options: Choose draft version, enable/disable format detection, enum suggestion, and required field marking
Generate: Click "Generate Schema" or press Ctrl+Enter (Cmd+Enter) to produce the schema
Review: Switch between Schema and Documentation views. Copy the result with the Copy button

Validate JSON

Enter Schema: Paste a JSON Schema into the left panel
Enter Data: Paste JSON data to validate into the right panel
Validate: Click "Validate" to check conformance. Errors show JSON Pointer paths for each issue

Multi-Sample Inference

Unlike most online schema generators that work with a single JSON sample, this tool supports multi-sample inference:

Optional Properties: A field present in all samples is marked required; a field missing from any sample is optional
Enum Detection: String fields with a small set of unique values across samples are suggested as enum constraints
Nullable Types: If a field is null in some samples, the schema uses ["string", "null"] type notation
Mixed Types: Fields with different types across samples generate oneOf schemas

Smart Format Detection

When enabled, the tool automatically detects common string patterns and adds format annotations:

date-time: ISO 8601 timestamps (e.g., 2025-01-15T10:30:00Z)
date: ISO 8601 dates (e.g., 2025-01-15)
email: Email addresses (e.g., user@example.com)
uri: HTTP/HTTPS URLs (e.g., https://example.com)
uuid: UUID format strings (e.g., 550e8400-e29b-41d4-a716-446655440000)
ipv4: IPv4 addresses (e.g., 192.168.1.1)
ipv6: IPv6 addresses

Supported Validation Keywords

Type: type (including arrays for nullable), enum, const
String: minLength, maxLength, pattern, format
Number: minimum, maximum, exclusiveMinimum, exclusiveMaximum, multipleOf
Object: properties, required, additionalProperties, patternProperties, minProperties, maxProperties
Array: items, minItems, maxItems, uniqueItems
Composition: oneOf, anyOf, allOf, not, if/then/else

Features:

🔧 Schema Generation: Generate JSON Schema from any JSON data (objects, arrays, primitives)
📊 Multi-Sample Inference: Add multiple JSON samples to auto-detect optional vs. required properties
🔍 Smart Format Detection: Automatically detect email, URI, date-time, UUID, IPv4, and IPv6 patterns
🎯 Enum Suggestion: Detect repeated string values across samples and suggest enum constraints
📝 Draft Support: Generate schemas for Draft 2020-12, Draft-07, or Draft-04
✅ JSON Validation: Validate JSON data against any schema with detailed JSON Pointer error paths
📖 Documentation: Auto-generate Markdown documentation from the generated schema
⚙️ Configurable: Toggle format detection, enum inference, required fields, and additionalProperties
🔒 Privacy First: All processing happens locally in your browser - no data sent to servers
⌨️ Keyboard Shortcut: Ctrl+Enter (Cmd+Enter) to generate or validate instantly

Common Use Cases:

API Development: Generate schemas from API response samples for OpenAPI/Swagger specs
Data Validation: Create schemas for validating configuration files or data pipelines
TypeScript/Code Generation: Use generated schemas as input for code generation tools
Documentation: Auto-generate property tables for API documentation
Testing: Validate test fixtures against expected schemas

References:
Tech Blog with curated related content
Web Tools Collection

Written by Hidekazu Konishi