JSON Schema → mock data generator

Generate mock JSON
from any JSON Schema.
Instantly.

Paste a JSON Schema and get a valid JSON instance with realistic example values. Draft-07 and 2020-12. Nested objects, arrays, multiple instances. Runs entirely in your browser.

Your data never leaves your browser
Realistic values — not "string_1"
1, 3, 5 or 10 instances at once
Ready for tests, Postman, Storybook
Always free
Need the reverse? JSON to JSON Schema converter
JSON Schema → Mock Data Generator   100% client-side
Paste a JSON Schema and get realistic mock data — ready for unit tests, Postman collections, Storybook fixtures and API documentation examples. Need to generate a schema first? JSON Schema Generator →
JSON Schema input
  Mock JSON ready 

      

 
    

  

 
  
  
When do you need mock JSON from a schema?

  
Four common workflows.

  

    

      
 API testing and fixtures

      
Generate realistic test fixtures from your OpenAPI or JSON Schema definitions. Use the mock data directly in unit tests, Postman collections or mock servers — without writing fixture data by hand.

    

    

      
 Frontend development

      
When the backend API is not ready, generate mock responses from the agreed schema. Seed your frontend app, Storybook components or UI tests with realistic data that matches the final structure.

    

    

      
 Schema validation testing

      
Generate a valid instance from your schema, then validate it against the schema with AJV to verify the schema itself is correct. A generated instance that fails validation reveals a bug in the schema.

    

    

      
 Documentation examples

      
OpenAPI docs, Confluence pages and README files need JSON examples alongside schema definitions. Generate realistic examples directly from the schema to keep them always in sync with the structure.

    

  

 
  

 
  


  
JSON Schema to sample data: $ref, enums and formats

  
The generator follows your schema the way a validator would: local references such as #/$defs/Address or #/definitions/Item are resolved (recursive references stop after one level), enum and examples values are used, format produces realistic emails, URIs, dates and UUIDs, "type": ["string", "null"] is understood, and every array item gets a different value within minItems/maxItems.
To create a schema from an existing document, use JSON to JSON Schema; for GraphQL SDL instead of JSON Schema, use GraphQL to JSON.




  
  
Related tools

  
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JSON to C#
Generate C# classes or records with System.Text.Json attributes.
All schema, apis & sql tools 

 
  
  
 
  

 
  
  

    
Frequently asked questions

    
Common questions about generating JSON from a JSON Schema.

 
    

      
How do I generate JSON from a JSON Schema?

      
Paste your JSON Schema into the input above and click Generate. The tool reads the type definitions and creates a valid JSON instance with realistic example values. Nested objects, arrays and required/optional fields are all handled automatically.

    

 
    

      
What is the difference between a schema and a JSON instance?

      
A JSON Schema is a blueprint — it describes what a JSON document should look like: which fields exist, their types and constraints. A JSON instance is actual data that conforms to that blueprint. This tool generates a valid instance from your schema blueprint.

    

 
    

      
Does the generator support Draft-07 and 2020-12?

      
Yes. The generator reads the $schema field and supports both versions. The core type keywords (type, properties, items, required) are identical between Draft-07 and 2020-12 — the generator handles both correctly.

    

 
    

      
Can I generate multiple mock instances at once?

      
Yes. Set Instances to 3, 5 or 10 and the output will be a JSON array with that many objects, each generated independently with slightly varied values — useful for seeding databases or populating frontend fixtures.

    

 
  
    

      
Does the generator resolve $ref?

      
Yes, local references (#, #/$defs/…, #/definitions/… and any JSON pointer). Remote URLs are not fetched, so everything stays in your browser.

    

    
  

 


				
	
		
	


			
		
				
	

	
		
		



 

	
	

	
	
	
	
			
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