JSON Schema Generator

Infer a standards-compliant JSON Schema from example data — formats, required keys, unions and additionalProperties control.

JSON Input

Node Details

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JSON Schema ●

Infer a standards-compliant JSON Schema from example data — formats, required keys, unions and additionalProperties control.

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Key Features

Format Detection

Strings matching email, date, date-time, uri and uuid patterns get their proper format annotation automatically.

Required Inference

For arrays of objects, only keys present in every element land in required — optional keys are detected, not forced.

Union Types

A field seen as both string and null becomes type: ["string","null"], never silently collapsed.

Draft Choice

Emit Draft 2020-12 or Draft-07 $schema URIs plus optional additionalProperties: false strictness.

How to Use JSON Schema Generator

1

Paste Example JSON

Provide a representative payload — ideally an array covering all shape variations.

2

Tune the Schema

Pick the draft, required strictness and additionalProperties mode.

3

Copy or Download

Use the schema in your validator, docs or code generation pipeline.

Technical Architecture & Privacy Comparison

How formatjson.net compares to traditional server-based JSON formatters and converters

100% Client-Side Execution Zero Server Upload RFC 8259 & RFC 4180 Compliant IEEE-754 64-Bit Int Safe JSON Schema 2020-12 Offline-Ready PWA
Capability / Standard formatjson.net (Client-Side Workbench) Traditional Server-Based Tools
Data Processing & Privacy 100% local in-browser JavaScript — payloads never leave your device Often uploads JSON/XML/CSV to remote backend servers
Confidential API Keys, JWTs & PII Safe by design — zero network transmission, works offline via Service Worker Risk of server access logs or third-party data retention
Broken & Truncated LLM JSON Repair 1-click lexical state machine fixes comments, single quotes, trailing commas, Python literals & unclosed brackets Fails with syntax error on non-strict JSON
64-Bit Snowflake IDs & Leading Zeros Preserves unsafe integers (> 2^53 - 1) and leading-zero codes ("00123") without precision loss Silently truncates 64-bit IDs or strips leading zeros
Deep Nested Array Exploration Interactive spreadsheet drill-down ([n items] →) with breadcrumbs, 3-state sorting & inline cell editing Flat root-only tables or read-only trees
Large File Responsiveness Chunked lazy tree (200 nodes/batch) + paginated table + 150 KB highlight guard Main-thread DOM freeze on multi-megabyte files

Frequently Asked Questions

Which JSON Schema drafts are supported? ▾

Both Draft 2020-12 and Draft-07 $schema URIs can be generated.

How is required computed? ▾

Inside object arrays, a key appears in required only if every element defines it — matching real-world optional fields.

Which string formats are detected? ▾

email, date, date-time, uri and uuid are recognized from value patterns.

Are mixed-type fields handled? ▾

Yes — conflicting types merge into JSON Schema union arrays like ["string","null"].

Can I get strict schemas? ▾

Enable the additionalProperties: false option to reject undeclared fields.