What Is This Tool For?
Working with raw JSON from an API response, a config file, or a database dump can be painful when it's all on one line. This formatter instantly structures your JSON into a readable, indented layout as you type — no button clicks, no page reloads.
It's built for developers who need to debug REST APIs, inspect webhook payloads, validate JSON configs before deployment, or just make sense of a messy data blob on the go. Works equally well on desktop and mobile, with horizontal scrolling so nothing gets squished.
Practical Examples
Example 1 — Debugging an API Response
You get a minified response from a REST endpoint and need to find a nested field fast. Paste it in and the formatter expands every level instantly, with keys highlighted in blue so they're easy to scan.
Input: {"user":{"id":42,"name":"Alice","roles":["admin","editor"]},"token":"abc123"}
Output:
{
"user": {
"id": 42,
"name": "Alice",
"roles": [
"admin",
"editor"
]
},
"token": "abc123"
}
Example 2 — Catching a Config Error Before Deployment
You edited a JSON config file manually and aren't sure if you left a trailing comma. Paste it in — the error banner will flag the exact line so you can fix it before it breaks your build.
Input: {"host":"localhost","port":5432,"debug":true,}
Error: ⚠ SyntaxError at line 1 — Unexpected token }
→ Check for a trailing comma before the closing brace.
FAQ
Does it send my JSON to a server?
No. Everything runs in your browser. Your data never leaves your device, which makes it safe to use with sensitive API keys or internal configs.
Why does the error message say "line 1" even for multi-line JSON?
The browser's built-in JSON parser reports the character position, not always the visual line. The tool converts that offset to an approximate line number — it's usually accurate within one or two lines for large inputs.
Can I format very large JSON files?
Yes, up to a few MB works fine in most modern browsers. For files over 5 MB, performance depends on your device. If it feels slow, try a desktop browser.
What does "Collapse All" do?
It folds every object and array into a single line so you can see the top-level structure at a glance. Click any ▶ arrow to expand individual nodes.
Does it work on mobile?
Yes. The output panel scrolls horizontally on small screens so deeply nested JSON stays readable without wrapping or squishing.