@jsonfmt/cli

Format, validate, diff, and inspect JSON from your terminal.

Zero dependencies. Colorized output. Runs anywhere Node.js runs.

Install

npm install -g @jsonfmt/cli

Or run instantly without installing:

npx @jsonfmt/cli '{"hello":"world"}'

Quick Start

# Format a file
jsonfmt data.json

# Pipe from stdin
echo '{"name":"Alice","age":30}' | jsonfmt

# Validate
jsonfmt --validate data.json

# Diff two files
jsonfmt --diff a.json b.json

# Get stats
jsonfmt --stats data.json

Output Example

$ echo '{"name":"Alice","age":30,"roles":["admin","user"],"active":true}' | jsonfmt

{
  "name": "Alice",
  "age": 30,
  "roles": [
    "admin",
    "user"
  ],
  "active": true
}

$ jsonfmt --stats data.json

  keys       3
  strings    1
  numbers    1
  booleans   1
  arrays     1
  objects    1
  depth      2
  bytes      65

$ jsonfmt --diff a.json b.json

  ~ age: 28 → 29
  + role: "admin"
  - email: "[email protected]"

All Options

| Flag | Description | Example | |------|-------------|---------| | (no flag) | Pretty-print with colors | jsonfmt data.json | | --minify | Compact single-line output | jsonfmt --minify data.json | | --sort-keys | Sort object keys A-Z | jsonfmt --sort-keys data.json | | --validate | Check validity (exit 0/1) | jsonfmt --validate data.json | | --stats | Count keys, types, depth, bytes | jsonfmt --stats data.json | | --diff <file> | Compare two JSON files | jsonfmt --diff a.json b.json | | --get <path> | Extract value by dot-path | jsonfmt --get "users[0].name" data.json | | --indent <n\|tab> | Set indentation (default: 2) | jsonfmt --indent 4 data.json | | --max-depth <n> | Truncate nested output | jsonfmt --max-depth 3 data.json | | --max-array <n> | Truncate long arrays | jsonfmt --max-array 5 data.json | | --no-color | Disable ANSI colors | jsonfmt --no-color data.json > out.txt | | --help | Show help | jsonfmt --help |

Use Cases

CI/CD pipelines — validate JSON configs before deploy:

jsonfmt --validate config.json || exit 1

API debugging — format curl responses:

curl -s https://api.example.com/users | jsonfmt

Extract values — pull fields from JSON files:

jsonfmt --get "database.host" config.json

Compare configs — diff staging vs production:

jsonfmt --diff staging.json production.json

Minify for storage — shrink JSON payloads:

jsonfmt --minify large.json > small.json

How It Works

Custom Lexer -> Parser -> AST pipeline (same engine as jsonfmt.dev):

Input string
  → Lexer (tokenize: strings, numbers, braces, colons)
  → Parser (build AST: objects, arrays, values)
  → Formatter (colorize + indent)
  → Terminal output

• Better error messages than JSON.parse — shows exact line and column
• Handles all JSON edge cases (unicode escapes, nested depth, large files)
• Zero dependencies — single 25KB file, no node_modules

Ecosystem

| Product | What | Link | |---------|------|------| | Web App | Full JSON toolkit (33 converters, 8 tabs, AI Helper) | jsonfmt.dev | | API | 63 REST endpoints for JSON processing | api.jsonfmt.dev/docs | | CLI | This package | npm i -g @jsonfmt/cli | | Chrome Extension | Auto-format JSON in browser tabs | Chrome Web Store | | Bookmarklet | One-click format on any page | jsonfmt.dev/bookmarklet |

Why Not Just Use jq?

| | jsonfmt | jq | |---|---|---| | Install | npm i -g @jsonfmt/cli | Separate binary, varies by OS | | Syntax | Familiar flags (--get, --diff) | Custom query language to learn | | Colors | Built-in, automatic | Requires --color-output | | Diff | --diff a.json b.json | Not built-in | | Validate | --validate with exit codes | jq . > /dev/null (workaround) | | Stats | --stats (types, depth, bytes) | Not built-in | | Deps | Zero | C binary |

Use jsonfmt for formatting, validating, and inspecting. Use jq for complex data transformations.

License

MIT

jsonfmt.dev — Format, validate, convert, diff, repair, and query JSON.