I work with JSON every day, and I kept getting frustrated with online JSON tools: slow pages, lots of ads, and many of them upload your data to a server. So I built my own set of tools: Online JSON Formatter.
👉 https://online-json-formatter-ten.vercel.app/
What makes it different
Private: everything runs in your browser. Your JSON is never uploaded.
Auto-fix: paste broken JSON and it repairs common mistakes – missing or trailing commas, single quotes, comments, unquoted keys, Python True/None, missing brackets – and tells you exactly what it fixed.
Fast: 100/100 on Google PageSpeed, no sign-up, no limits.
The tools
Format & check: JSON Formatter (Code, Tree and Graph views), JSON Viewer, JSON Validator with the exact error line, JSON Schema Validator.
Convert: JSON ↔ CSV, JSON to Excel (real .xlsx), JSON ↔ XML, JSON ↔ YAML, JSON ↔ SQL.
Generate code: JSON to TypeScript, Python (dataclass / Pydantic), Java, and a JSON Schema generator.
More: JSON Compare, Text Compare, JSONPath tester, JWT decoder, Base64 and URL encode/decode, JSON minifier, sorter and repair.
There is also a free library of JSON datasets (countries, currencies, HTTP status codes, mock API data) and beginner guides like JSON in Python and JSON.parse in JavaScript.
Tech
React + Vite, every page prerendered for speed and SEO, deployed on Vercel. The JSON repair works by walking the text character by character, so it never changes the text inside your strings.
I would love your feedback: what tool should I add next? 🙂
