Messy input
{"id":1,"name":"Ada","tags":["x","y"],"active":true}About the JSON Formatter playground
The JSON Formatter validates and pretty-prints JSON, turning a single dense line into a readable, indented tree. It reveals the structure of nested objects and arrays, and flags syntax errors such as trailing commas or unquoted keys. The tool can also minify JSON back to a compact form. All of this runs in your browser, so API responses or config files containing sensitive values are never uploaded.
JSON (JavaScript Object Notation) is a lightweight, language-independent data format built from key/value objects, arrays, strings, numbers, booleans, and null. It is the default format for REST APIs, configuration files, and data interchange between services. Because JSON is usually transmitted compactly, formatting it is essential for inspecting payloads, debugging requests, and verifying structure. A formatter also acts as a quick validator that catches malformed data before it breaks your code.
HostedJSON Formatter runtime
mainentry file
single fileworkspace
stdinprogram input
How it works
1
Write
The main file is the entry point for each run.
2
Give it input
Use the Input panel to pipe standard input to your program when it needs data.
3
Run
Run sends your code to a fresh hosted runtime and streams the result into the output panel.
4
Keep or share
Your draft stays in this browser, and Share creates a separate snapshot link.
External resources
- json.org— Format reference
Formatted output
{
"id": 1,
"name": "Ada",
"tags": [
"x",
"y"
],
"active": true
}Minified output
{"id":1,"name":"Ada","tags":["x","y"],"active":true}Nested object messy input
{"user":{"id":1,"address":{"city":"Paris","zip":"75001"}},"roles":["admin","editor"]}Nested object formatted output
{
"user": {
"id": 1,
"address": {
"city": "Paris",
"zip": "75001"
}
},
"roles": [
"admin",
"editor"
]
}Array of objects formatted
[
{
"id": 1,
"name": "Widget",
"price": 9.99
},
{
"id": 2,
"name": "Gadget",
"price": 19.5
}
]Mixed types formatted
{
"count": 42,
"ratio": 0.75,
"enabled": false,
"label": null,
"items": []
}Escapes and unicode formatted
{
"path": "C:\\tmp\\log.txt",
"quote": "She said \"hi\"",
"city": "caf\u00e9"
}Deep nesting formatted
{
"data": {
"items": [
{
"id": 1,
"meta": {
"tags": [
"a",
"b"
]
}
}
]
}
}How it works
The editor uses Monaco, the engine behind VS Code, with language-aware editing tools and familiar keyboard controls.
What it does
Paste JSON and it validates and pretty-prints it into a readable, indented tree.
Nested objects and arrays are expanded so the structure is clear.
Can also minify formatted JSON back to a compact single line.
Validation and options
Flags syntax errors like trailing commas or unquoted keys.
Acts as a quick validator to catch malformed data before it breaks code.
Switch between pretty-print and minify as needed.
Privacy
All processing runs in your browser; API responses are never uploaded.
Config files with sensitive values stay on your machine.
Tips
Copy the formatted JSON to inspect payloads or debug requests.
Use it to verify structure before pasting into your app.
Every shortcut, searchable:
Editing
Undo
Ctrl+Z
Redo
Ctrl+⇧+Z
Select next occurrence
Ctrl+D
Delete line
Ctrl+⇧+K
Move line up / down
Alt+↑ / ↓
Copy line up / down
Alt+⇧+↑ / ↓
Toggle comment
Ctrl+/
Indent line
Ctrl+]
Outdent line
Ctrl+[
Navigation
Find
Ctrl+F
Find & replace
Ctrl+H
Go to line
Ctrl+G
Go to symbol
Ctrl+⇧+O
Selection
Select all
Ctrl+A
Select line
Ctrl+L
Select all occurrences
Ctrl+⇧+L
Shortcuts follow your OS — ⌘ becomes Ctrl on Windows and Linux.
It validates JSON and pretty-prints it into an indented, readable tree, and can also minify it back to a compact single line.
No. Formatting and validation run entirely in your browser, so API payloads and config data never leave your device.
Yes, it is completely free with no account and no usage limits.
Use the beautify option to expand JSON with indentation, or the minify option to strip all whitespace into a compact string.
Strict JSON disallows trailing commas, comments, single quotes, and unquoted keys. The formatter flags these so you can fix the syntax before using the data.
Inputpaste, type or drop a file
1 line251 Bformats as you type
Formatted JSON appears here as you type
ready