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JSON Formatter — Free Online Tool
JSON is the default data format for APIs, configuration files and web apps, but raw responses are often a single unreadable line. This JSON formatter parses whatever you paste and rewrites it with four-space indentation so objects and arrays become easy to scan, or compresses it into the smallest possible form with the Minify button. Because the tool uses the browser's own JSON parser, it doubles as a validator: if the text contains a trailing comma, single quotes, an unquoted key or a missing bracket, you get an Invalid JSON warning instead of silently broken output. Developers use it to read API responses from Postman or curl, debug configuration in package.json and tsconfig, prepare payloads for tests and clean up logs before filing a bug report. Minified JSON saves bytes in network requests and embedded scripts, while formatted JSON is better for code review. Processing happens locally in your browser, which matters when the data contains customer information, tokens or internal API structures, since nothing is uploaded to a server. Very large files of many megabytes can slow down a tab, so split them if the page becomes unresponsive. The formatter handles standard JSON only; comments and trailing commas are not valid JSON and must be removed first.
Use our JSON Formatter on AllConvertor — no registration, no download, works on iPhone, Android, Windows, and Mac. All processing runs in your browser when possible for maximum privacy and speed.
How to use JSON Formatter
- Paste your JSON text into the editor box.
- Click Format to beautify it, or Minify to compress it.
- Fix the highlighted syntax issue if an Invalid JSON alert appears.
- Copy the cleaned JSON into your project or API client.
Key benefits
- ✓ 100% free — no paywall or trial limits
- ✓ No account or email required
- ✓ Mobile-friendly responsive design
- ✓ Instant results in your browser
- ✓ Secure — data stays on your device
- ✓ Trusted by thousands of users daily
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Frequently Asked Questions
How do I format JSON online?
Paste your JSON into the box and click Format. The text is rewritten with four-space indentation so nested objects and arrays are easy to read.
How can I check if my JSON is valid?
Click Format or Minify. If the JSON has a syntax error such as a trailing comma, single quotes or a missing bracket, an Invalid JSON message appears.
What does minify do?
Minify removes all unnecessary spaces and line breaks to produce the smallest valid JSON, useful for network payloads and embedded data.
Is my JSON uploaded to a server?
No. Parsing and formatting happen in your browser, so private or sensitive data never leaves your device.
Why does valid-looking JSON show an error?
Strict JSON requires double quotes around keys and strings, no trailing commas and no comments. JavaScript object literals often break these rules.