About SmartJson
Santhi
Santhi builds and maintains SmartJson and runs every error message on this site through the real parsers before publishing it.
Why SmartJson exists
It started as a personal tool. Day-to-day work meant reformatting API responses, finding out why a YAML pipeline file would not parse, and diffing two exports to find the one changed row. The popular online tools for this sent the pasted data to their own servers.
That is a real problem when the data is an access token, a customer export or an internal config file. So every SmartJson tool does its work in JavaScript inside your browser tab. There is no upload endpoint behind the formatters, validators, converters or compare tools.
The site grew from one JSON formatter into the current JSON, XML, CSV and YAML tools, each added because it was needed for real work. The newest parts are JSON Repair, which lists every change it makes, and JSON Error Messages, Decoded, which shows what each browser and language actually prints for the same broken JSON.
Your data
What you paste into a tool stays in your browser and is never uploaded or stored. Share links keep their data after the # in the address, which browsers never send to a server. The details are in the Privacy Policy.
How it is tested
Parsing uses established open-source libraries: js-yaml for YAML, fast-xml-parser for XML, Papa Parse for CSV and jsonrepair for broken JSON. Unit tests and Playwright browser tests run on every change, and a change does not ship until they pass.
The error messages quoted on this site are captured by a script that runs the same broken inputs through Chrome, Firefox, Safari's engine, four Node versions, Bun and three Python versions. A unit test fails if Node ever prints something different from what the pages say. How we test has the full list and the script.
How it is funded
The tools are free and will stay free, with no account and no limits. We plan to show Google ads to pay for hosting. Ads never see what you paste into a tool, because it never leaves your browser. The Cookie Policy explains the cookie choice.
What changed recently
Every change that affects what you see is listed in the changelog, with its date.
Contact
Found a bug, or a file a tool handles wrongly? Write to support@smartjson.io or use the contact page. Reports with a sample input are the most useful, and Santhi answers them.