What is a JSON viewer?

A JSON viewer displays structured JSON in a readable format, often with a collapsible tree, search and validation.

How do I format JSON online?

Paste your JSON into Tool Kumar. The formatter creates an indented view, while the validator reports syntax errors.

Is this JSON viewer private?

Yes. Parsing and formatting happen in your browser, so your document does not need to leave your device.

Can I validate a large JSON file?

Yes. The viewer is designed for large documents and keeps the input local while it parses the file.

Tool Kumar blog

JSON guides, tips and history

Clear, practical writing for developers who read, debug and ship JSON every day. Each post links to the free JSON viewer, so you can try every example as you read.

json-formatting-guide.json

{
  "valid": true,
  "indent": 2,
  "errors": []
}

Guide · 6 min read

How to format and validate JSON: a practical guide

Understand valid JSON, track down syntax errors and choose readable formatting for APIs, config files and logs.

October 13, 2026

origin-of-json.json

{
  "name": "JavaScript Object Notation",
  "standards": ["RFC 8259", "ECMA-404"]
}

History · 9 min read

The origin of JSON: the story behind the format

Follow JSON from a small browser messaging idea to the language-independent standard behind modern APIs.

October 13, 2026