Hey Product Hunt! 👋 I built jsonfmt.dev because I was frustrated with existing JSON tools — they're either bloated with ads, require an account, send your data to a server, or just look terrible. My goal was simple: the fastest, cleanest JSON tool that works entirely in your browser. No backend. No tracking. No data ever leaves your machine. What started as a formatter quickly grew as I kept hitting my own pain points: - Pasting a JWT and having to open a second tab to decode it - Copying JSON to a separate YAML converter - Manually hunting for that one misplaced comma in 500 lines of JSON So I kept adding tabs — Diff, Convert (YAML/CSV/XML/TOML/Python/Go), JWT Decoder, Repair (fixes trailing commas, unquoted keys, Python literals), Schema Validator, JSONPath Evaluator, and JSONL Viewer. All offline-capable as a PWA. The whole thing is a single HTML file with zero external dependencies — it works on file:// with no internet connection. The source is open on GitHub. Would love your feedback — especially on what tools you reach for most when working with JSON! 🙏 --- Tips before submitting: - Swap 👋 emoji for text-only if you prefer a more professional tone - Add a specific user anecdote if you have one ("A teammate once spent 2 hours debugging a trailing comma…") - Mention it's free — Product Hunt audiences respond well to that

jsonfmt.dev

Format, validate, diff, convert JSON. 100% client-side.

Format, validate, diff, convert JSON. 100% client-side.