About JSON Hearth
Developer tools that keep your data with you.
JSON Hearth is a collection of focused tools and practical guides for viewing, validating, comparing and transforming JSON, JSONL and adjacent developer-data formats.
Why it exists
Everyday data work should not require creating an account or uploading an API response, log file or configuration document to an unknown server. The tools here are designed to run in your browser so the data you paste or open stays on your device.
What you can do
Open JSON and JSONL, format or repair documents, compare payloads, test JSONPath expressions, validate schemas, convert CSV and YAML, and generate useful TypeScript, Go and Java types. Each guide is linked to the tools that support the workflow it explains.
Browse all tools →How the guides are maintained
Guides are written around concrete developer tasks rather than a target word count. Worked examples, limitations and edge cases are added when they help explain the problem. A guide shows an updated date only after its content has been materially revised; reading time is calculated from the page instead of being assigned by hand.
Read the JSON guides →What “local” means
Tool input is processed by code running in the browser tab. It is not sent to an application server, saved to an account or used for model training. The site itself may use analytics and advertising; those services do not receive the JSON, JSONL, CSV, YAML or JWT content entered into the tools.
Editorial approach
The knowledge base is maintained alongside the tools so examples can be checked against the workflows they describe. Content is revised when a topic needs more context, a limitation needs to be made clearer or a worked example can make the answer more useful. The goal is a practical reference for developers, not a collection of pages created to hit a publishing quota.
Open implementation
The application source is public so developers can inspect how the browser tools work, verify privacy-sensitive behavior and report a reproducible issue against the implementation rather than relying only on marketing claims.
View the JSON Hearth source on GitHub →