JSON Formatter

NasseoTools JSON Formatter

NasseoTools JSON Formatter helps you beautify, validate, and review JSON in one place. Paste your JSON text or upload a file, and the tool instantly formats it into a clean, readable layout—perfect for debugging, sharing, or preparing API responses.

Format JSON in seconds

Turn messy JSON into a tidy structure with your preferred indentation:

• 2 spaces
• 3 spaces
• 4 spaces

Validate JSON with clear error messages.

If your JSON has a problem (missing commas, broken brackets, or incorrect quotes), the validator points out the issue with easy-to-understand errors so you can fix it faster.

Explore your JSON in Tree View

Navigate large JSON files easily using Tree View, which collapses and expands objects and arrays.

Extra feature: image preview on hover for Image URLs inside the tree—great for checking JSON that contains media links.

Debug with Graph View

Use Graph View to visualize arrays and objects, making it easier to spot structural issues and correct data quickly.

Upload, download, print, and share.

Work the way you like:

• Upload a JSON file to format it
• Download the formatted JSON file
• Print JSON data when needed
• Save and share formatted output with others

Auto-update formatting

Enable Auto Switch to format automatically while you type, or turn it off if you prefer manual formatting.

Works great for API JSON

JSON is widely used for client-server communication, so this tool is ideal for quickly formatting APIs during testing or cleanup.

Local save for your last formatted JSON

Your last formatted JSON is stored locally in your browser (Local Storage), so you can continue from where you left off—like a lightweight alternative to editors such as Notepad++, Sublime Text, or VS Code for quick JSON cleanup.

JSON lint and quick fixes

This tool also works as a JSON lint/format checker. If your JSON has missing quotes or common format issues, use the settings (screwdriver) icon to apply quick fixes and correct the structure.

JSON Validator

JSON Validator Online helps you check whether your JSON is valid and ready to use. It scans your data against the JSON standard (RFC format rules) and highlights any syntax issues so you can fix them quickly.

Find errors faster with line-by-line highlights.

When something is wrong, the validator shows exact line numbers and a clear error message. It makes it easy to spot missing commas, extra brackets, broken quotes, and other common mistakes.

Fix JSON instantly with the Screwdriver tool.

Use the Screwdriver icon as a quick JSON Fixer to repair common formatting and syntax errors—saving time when you’re working with messy data.

No installs, no sign-up, works anywhere.

• Works online with just an internet connection
• No software to install
• No account needed

Safe and fast in your browser

Your JSON is validated directly in your browser, keeping the process quick and convenient as you work.

JSON Lint made simple

Whether you’re debugging an API response or cleaning up a JSON file, this tool gives you a fast, accurate JSON validity check in seconds.