---
title: "About JSON Lark | JSON Lark"
description: "What JSON Lark is: free JSON type generators, a JSONPath tester, JSON Patch and flatten tools that run entirely in your browser. How it works."
url: https://jsonlark.me/about/
---

Sheet 09 About

# About JSON Lark

A small set of tools for the work around JSON data: describing it as types, querying it and changing it.

## What it does

JSON Lark turns JSON samples into types for TypeScript, Go, Python, Rust and C#, tests RFC 9535 JSONPath queries, generates and applies RFC 6902 JSON Patches and RFC 7396 merge patches, and flattens nested JSON into path keys and back. Types are the blueprints of your data, hence the drafting-table look.

## How it works

Every tool is JavaScript that runs in your browser tab. Nothing you paste, type or open is sent to a server; the pages keep working offline once they have loaded.

- The type generators share one inference core written for this site. It folds every sample into one shape, notes which keys are missing from some objects and which values are sometimes null, then prints that shape in each language's own conventions.
- JSONPath queries run on [json-p3](https://github.com/jg-rp/json-p3) (MIT licence) in its strict, standard-only mode.
- JSON Patch, merge patch and JSON Pointer are implemented here and tested against the examples in their RFCs. They and the flattener are also checked against randomly generated documents that must survive a round trip.

## Who is behind it

JSON Lark is one of a family of free, single-purpose tool sites. It has no accounts, no ads and no tracking cookies. If something looks wrong, the generated code is easy to check: every tool shows exactly what it produced.

## Related tools

To repair or format broken JSON, use [JSONMender](https://jsonmender.me/). For JSON Schema, and schema-to-TypeScript conversion, see [SchemaStash](https://schemastash.me/).