Your JSON never leaves your machine

Holo Dev — Wed, 26 Aug 2026 11:35:10 +0000

I keep a tab with a JSON formatter open roughly 300 days a year. And roughly 300 days a year, that tab tries to sell me something.

So I built jsonkit.tools — 24 browser-based dev tools under one roof. The browser tools run client-side. No signup, no upload. You paste, you get the result.

What's actually in there

JSON formatter with tree view, validators, converters between JSON/CSV/YAML/XML (both directions), Base64 and URL encoding, JSON diff, JSON-to-TypeScript, UUID and hash generators, and a timestamp converter. Each tool is its own page with its own URL — no SPA tab-switching.

The less common part: a REST API

Most browser tool sites stop at the browser. I added api.jsonkit.tools — 28 endpoints with the same operations you get in the UI. The endpoints follow the same input/output contract.

Why? Because if you're building automation or working with LLM agents, you want deterministic transformations — not a model guessing how to reformat your payload. One HTTP call, stable output, no surprises.

curl -X POST https://api.jsonkit.tools/v1/json/format \
  -H "Content-Type: application/json" \
  -d '{"input": "{\"a\":1,\"b\":2}", "indent": 2}'

Stack

Astro with static generation. Each tool compiles to its own HTML page — fast to load, easy for search engines to index, and with zero client-side routing overhead. Dark theme by default.

The tools themselves are vanilla JS components. No heavy framework runtime, no hydration penalty for what is essentially a text box and a function call.

jsonkit.tools — feedback welcome.

DEV Community: Holo Dev

Your JSON never leaves your machine

What's actually in there

The less common part: a REST API

Stack