JSON formatter and validator
Format, validate, and minify JSON in the browser with syntax highlighting and error feedback.
JSON Kit
JSON Kit is a browser-based suite of more than 40 JSON tools for developers, covering formatting, validation, conversion to TypeScript, Zod, and other formats, plus repair and inspection tools for AI-generated or API JSON. Core tools are free, run client-side, and do not send data to servers.
Overview
JSON Kit is a browser-based collection of JSON utilities for developers working with APIs, configuration data, and AI-generated structured output. The site groups more than 40 tools into core workflows such as formatting, validation, conversion, repair, and inspection.
Its main purpose is to reduce manual type and schema work around JSON. You can format or validate payloads, generate TypeScript or Zod from sample data, convert JSON into other code and schema formats, and repair malformed JSON produced by LLMs, all without sending data to a server.
Core capabilities
Broad converter library
Convert JSON samples into TypeScript interfaces, Zod schemas, Pydantic models, Go structs, Rust structs, Kotlin classes, Swift structs, Java POJOs, C# classes, GraphQL, JSON Schema, SQL, Supabase, YAML, XML, CSV, mock data, and .env formats.
LLM JSON repair tools
Repair malformed AI-generated JSON and extract JSON from markdown blocks produced by LLMs.
Runtime schema generation
Generate named, split Zod schemas with `z.infer` type exports and optional format detection for values such as email, UUID, datetime, and URL strings.
Inspection and transformation tools
Inspect and compare payloads with JSON Diff, JSONPath Tester, JSONL Viewer, JSON Flattener, and JSON to CSV utilities.
Client-side processing
Work entirely in the browser using Monaco Editor, with support for large files and no server upload on the core tools.
Common workflows
Read and debug JSON responses
Paste API responses or webhook payloads into the formatter to make them readable, catch syntax errors, and inspect the structure before debugging downstream code.
Generate types and validators
Turn sample payloads into TypeScript interfaces or Zod schemas when you need types and runtime validation for an API client or frontend app.
Clean up LLM output
Repair malformed JSON from ChatGPT, Claude, or similar tools, then extract embedded JSON from markdown blocks for reuse in code or data pipelines.
Inspect and transform data
Compare two JSON objects, flatten nested data, query paths, or convert arrays into CSV when you need to inspect payloads or move data into another format.
Derive code and schema artifacts
Use the wider converter set to generate schemas or stubs for languages and formats such as Pydantic, Go, Rust, Kotlin, Swift, Java, C#, GraphQL, YAML, XML, SQL, Supabase, or .env.
Pros and Cons
Pros
- Core tools are free forever and do not require sign-up.
- Processing happens in the browser, so data stays on the device for the documented core workflows.
- The toolset covers several adjacent JSON tasks in one place, including formatting, validation, conversion, repair, and inspection.
- The TypeScript and Zod generators produce structured output designed for real codebases, not just one-off snippets.
- The site explicitly supports large files, with the formatter page stating that files around 50MB+ can usually be handled.
Cons
- The Pro plan is only announced as coming soon, so the public pricing page does not yet show final Pro pricing or limits.
- The source does not document every export target, integration, or workflow in detail, so some advanced capabilities may need confirmation on the product site.
FAQ
Do I need to create an account to use JSON Kit's free tools?
JSON Kit runs in the browser, so there is no account requirement for the free tools. The pricing page says the core tools are free forever and available with no sign-up needed.
What kind of output does JSON Kit generate?
The generated output can be copied into code files directly. The JSON to TypeScript tool produces interfaces or type aliases, and the JSON to Zod tool produces named schemas with `z.infer` type exports.
Which workflows does JSON Kit cover?
JSON Kit is built for browser-side use with common developer workflows: formatting and validating JSON, converting JSON to TypeScript, Zod, Pydantic, and other code or schema formats, and repairing malformed LLM JSON.
Is there a paid plan?
The source pages show browser-side processing for the core tools and mention free core tools plus a Pro plan coming soon for AI-powered features such as Describe to JSON. The page does not list exact Pro pricing yet.
What are the main limits or considerations?
The product pages mention use with API responses, AI-generated output, configuration files, and large JSON payloads. The formatter page says the Monaco Editor handles files up to about 50MB+, while the site emphasizes that data does not leave the browser.
Quick Facts
- Category
- Developer Tool
- Primary use
- JSON formatting, validation, and conversion
- Platform
- Browser-based web app
- Source domain
- jsonkit.co
- Pricing model
- Free core tools; Pro coming soon
- Privacy model
- Core tools run client-side with no server upload
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