A json formatter and validator built for developers, homelab engineers, and anyone who works with APIs, configs, or data pipelines. Paste raw or minified JSON, hit Format & Validate, and get instant syntax highlighting, a collapsible tree view, error detection with exact line and column numbers — all without sending a single byte to any server.
What This JSON Formatter and Validator Does
This tool covers the full workflow of working with JSON data:
🎨 Syntax highlighting — keys, strings, numbers, booleans, and null values are colour-coded for instant readability.
🌲 Collapsible tree view — switch from the code view to an interactive tree where you can expand, collapse, and search nodes by key or value. Nodes deeper than level 2 are collapsed by default to keep large structures manageable.
🔍 Key and value search — type in the search box to highlight matching nodes across the whole tree. All parent paths auto-expand so nothing is hidden.
⚠️ Error detection with position — if your JSON is invalid, the json formatter and validator shows the exact error message plus the line number and column where parsing failed. No more hunting through 500 lines of minified JSON.
📊 Stats bar — instantly see total key count, max nesting depth, formatted size, and counts of strings and numbers.
📋 Copy and download — copy the pretty-printed version, copy the minified version to clipboard, or download the result as a .json file.
How to Use It
- Paste your JSON into the input textarea — or click Load Sample to explore the tool with a pre-built example.
- Click ⚡ Format & Validate (or press
Ctrl+Enter) to parse and render the output. - Switch between Code and Tree view using the tabs above the output.
- In Tree mode, use the search bar to find keys or values, and the Expand All / Collapse All buttons to navigate large structures.
- Use 📋 Copy, 📋 Minified, or ⬇ Download to export the result.
The Minify button also works in reverse — it replaces the content of the input textarea with the compact single-line version of your JSON.
Why a Browser-Based JSON Formatter and Validator?
When you’re debugging an API response, reviewing a Home Assistant automation config, or checking a docker-compose.json export, you want answers fast — not a round trip to some cloud service that logs your data.
This json formatter and validator runs entirely in your browser using the native JSON.parse() engine. There is no backend, no analytics on your input, and no rate limits. It works offline once the page loads.
Practical Use Cases
🔌 Debugging REST API responses — paste the raw response body and immediately see its structure, key names, and value types without formatting it manually.
🏠 Home Assistant config inspection — HA exports automations, scripts, and dashboards as JSON. This json formatter and validator makes it easy to navigate nested conditions and action blocks in tree mode.
🐳 Docker and container configs — review docker-compose overrides, Portainer stack exports, or Traefik dynamic config files. If you’re new to containers, the Docker basics guide is a solid starting point.
📡 Validating webhook payloads — copy a raw webhook body from your logs and instantly check whether it’s valid JSON before writing a parser.
🛠️ Building and testing tools — need another browser-based tool? Take a look at the vCard QR Code Generator — same philosophy, zero server.
The official JSON specification defines the exact grammar this json formatter and validator validates against. Under the hood it uses the browser’s JSON.parse() — the same engine your JavaScript runtime uses, so what validates here will parse in your code.
Privacy, Ads, and Data Policy
- ✅ 100% free — no account, no registration
- ✅ No data storage — your JSON never leaves the browser tab
- ✅ No ads in results — no watermarks, no tracking pixels
- ✅ Client-side only — zero external API calls, works offline after initial page load
Open Source and Self-Hosting
The tool is a single folder — index.html, style.css, and script.js — with no build step and no dependencies. Drop it behind any static file server or into a WordPress page template and it works immediately.
Browse all tools at vahac.com/tools/.