Free Custom CSV & JSON Schema Builder
Create complex, deeply nested JSON structures or custom-column CSV files. Define what every single field should be, pick from over 40+ unique data types, preview your data instantly, and generate millions of rows. Entirely free, totally unlimited, and 100% secure.
Why use our Schema Builder limitlessly?
1. Unrestricted & Free
Most other tools restrict you to 1,000 rows. With BlobForge, if your browser can handle it, you can generate 100,000 or 1,000,000 rows for free.
2. Ultra-Fast Web Workers
BlobForge uses Web Workers to process data in the background, keeping your browser responsive even when generating gigabytes of JSON or CSV arrays.
3. High Privacy
Zero server uploads. Generated data never goes to any cloud provider or database. Total compliance with zero risk.
4. 40+ Fake Data Types
Generate financial records, IBANs, addresses, geolocation coordinates, IP addresses, names, custom lists, and precise timestamps.
How to Create a Custom Schema
Select Your Format
Head to the main generator page and pick either CSV or JSON.
Toggle Schema Builder
Check the "Use Schema Builder (define your own columns)" box to unlock the visual drag-and-drop editor.
Define Your Fields
Add custom columns, search and set the data types for each, and configure data limits. Drag and drop to reorder the structural output.
Generate Instantly
View real-time previews to make sure everything matches your database. Set the number of rows and click transmit.