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Format, Validate & Minify JSON Instantly

Paste raw, minified or messy JSON and get clean, indented, readable output in one click — or minify it back down to a single line for production. When the JSON is broken, the validator tells you exactly what is wrong and where: the error message and the line and column position, so a missing comma in a 5,000-line config takes seconds to find instead of an afternoon. Everything runs locally in your browser; your data never leaves the tab.

Indent Format = pretty-print · Minify = one line · Validate = check only. Errors show line:column.

🔒 100% private: everything runs inside your browser — nothing is uploaded, stored or logged.

How it works

Paste your JSON into the input box — pretty-printed or minified, any size.
Choose an indentation style: 2 spaces, 4 spaces or tabs.
Press Format to pretty-print, Minify to compact, or Validate to check without changing anything.
Copy the result or download it as a .json file. Errors show the exact line and column.

Features

Precise error reporting

Broken JSON returns the parser's message plus the line and column — no more hunting for a stray comma.

Three indentation styles

2 spaces for compactness, 4 for readability, tabs for your team's linter — minify for production.

Validate without rewriting

A validate-only mode checks syntax and leaves your formatting untouched.

Handles big payloads

The native browser JSON parser is fast — config files, API responses and exports of several megabytes are fine.

100% local

Parsing happens in your browser with the standard JSON engine. Secrets in payloads — tokens, keys — never touch a server.

Input & output. Input: any JSON text (RFC 8259) — objects, arrays, nested structures, numbers, strings, booleans, null. Output: formatted or minified JSON, viewable in the page, copyable, downloadable as .json.

Common use cases

Debugging API responses and webhook payloads copied from dev tools.
Pretty-printing minified config files (package.json, tsconfig, CI settings) before editing.
Minifying JSON before committing it or embedding it in a page.
Checking a JSON-LD structured data block before publishing it on a website.

Limitations (honest ones)

The tool formats standard JSON only: comments are invalid (JSON5/JSONC users must strip them first), duplicate keys are kept as the parser sees them, and very deep nesting (thousands of levels) can hit the browser's recursion limits. Large numbers keep the exact text you pasted only when re-serialized within JavaScript's number precision.

Frequently asked questions

Is my JSON sent to a server?

Never. Formatting uses your browser's built-in JSON parser, running entirely on your device — even offline.

Why does my JSON fail even though it looks fine?

The usual suspects: single quotes instead of double, trailing commas, unquoted keys, and smart quotes pasted from a word processor. The error position will point you at the offender.

Does it support JSON5 or comments?

No — standard JSON only. Comments are not part of the JSON spec; remove them (or use a JSON5 tool) before formatting.

How big a file can it handle?

Files of several megabytes format in well under a second on a modern machine. Beyond ~50 MB you may hit browser memory limits.

What is the difference between Format and Minify?

Format adds indentation and line breaks for humans; Minify strips all optional whitespace to produce the smallest valid equivalent — what you want in production.

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On mobile?

Working from your phone?

This tool runs in any mobile browser — no app needed. And for the image & PDF side of the toolbox, the CompressoPanda Android app ships 36 tools that run with no connection at all: compression to target size, editing and PDF essentials included.

Explore the Android App Google Play ↗