Best JSON Formatter and Viewer Tools for Developers

JSON formatting (also called "pretty-printing" or "beautifying") adds indentation and line breaks to compact JSON, making it readable. Viewing is a step further — presenting JSON as an interactive, collapsible tree rather than flat text.

Whether you are debugging an API response, exploring a data file, or reviewing a configuration, the right tool makes a significant difference. Here are the best options by category.

What is JSON Formatting?

Minified (compact) JSON removes all whitespace to save bytes:

{"name":"Alice","age":30,"city":"London"}

Formatted (pretty-printed) JSON adds indentation for readability:

{
  "name": "Alice",
  "age": 30,
  "city": "London"
}

Both are valid JSON. Minified is better for network transmission; formatted is better for humans.

Online JSON Formatters

JSONLint

JSONLint is the most widely known online JSON tool. It validates and formats JSON simultaneously — paste your JSON, click Validate, and get both a formatted output and any syntax errors highlighted. The clean interface makes it a go-to for quick checks.

• Validates and formats in one step
• Shows exact line numbers for errors
• No ads, no registration

JSON Formatter & Validator (jsonformatter.org)

A feature-rich online tool that offers tree view, raw view, and minification. The tree view lets you collapse and expand nested objects and arrays, which is invaluable for exploring large JSON structures.

• Interactive collapsible tree view
• Side-by-side tree and text views
• Minify (compact) option
• URL import — paste an API URL to fetch and format directly

JSON Crack

JSON Crack renders JSON as an interactive node graph — each key-value pair becomes a node connected by lines. This is particularly useful for understanding relationships in deeply nested structures that are hard to follow in a flat text view.

• Visual graph representation
• Zoom and pan on large structures
• Export diagram as image

Browser Extensions

JSON Formatter (Chrome/Firefox)

This extension automatically formats any JSON response you view in the browser. When you open an API URL directly, instead of seeing raw text, you get a formatted and collapsible tree view. There is no button to click — it just works.

Best for: developers who frequently call API endpoints in the browser tab.

JSON Viewer Pro

A more feature-rich browser extension that adds theme support, search within JSON, and copy-path functionality (click on any value to copy its full JSON path like users[0].address.city).

Best for: navigating large nested API responses with many layers.

IDE Plugins

VS Code — Built-in

VS Code formats JSON files automatically with no extensions needed. Open a .json file, press Shift+Alt+F (Windows/Linux) or Shift+Option+F (Mac), and the entire file is instantly formatted according to your indentation settings.

VS Code also highlights JSON syntax errors in real-time with red underlines and error messages in the Problems panel.

Prettier

Prettier is the most widely used code formatter in web development. It handles JSON alongside JavaScript, TypeScript, HTML, CSS, and more. Configure it once in your project and all JSON files are automatically formatted consistently.

npm install --save-dev prettier

# Format a single file
npx prettier --write data.json

# Format all JSON files in the project
npx prettier --write "**/*.json"

Command-Line Tools

Python's json.tool

Python ships with a built-in JSON formatter — no installation needed:

# Format a file
python -m json.tool data.json

# Format and save
python -m json.tool data.json > formatted.json

# Format piped input (e.g., from curl)
curl -s https://api.example.com/data | python -m json.tool

jq

jq is a powerful command-line JSON processor. It can format, filter, transform, and query JSON from the terminal. It is the Swiss army knife for JSON on the command line.

# Install on Mac
brew install jq

# Pretty-print
cat data.json | jq '.'

# Extract a specific field
cat data.json | jq '.users[0].name'

# Filter array by condition
cat data.json | jq '[.users[] | select(.age > 25)]'

Node.js one-liner

node -e "process.stdout.write(JSON.stringify(JSON.parse(require('fs').readFileSync('data.json')), null, 2))"

When to Use Each Tool