JSON Formatter Offline — v4

JSON Formatter Offline is a simple developer utility for validating, formatting, and minifying JSON data directly inside Firefox.

All JSON processing is performed locally. The extension does not upload your JSON content to a server.

• Validate JSON syntax.
• Display an error message when JSON is invalid.
• Format JSON with readable indentation.
• Minify JSON into a single compact line.
• Copy processed JSON to the clipboard.
• Process JSON without an Internet connection.
• No account or registration is required.

1. Click the JSON Formatter Offline icon on the Firefox toolbar.
2. Paste or type JSON into the input field.
3. Click Format to create readable, indented JSON.
4. Click Minify to convert the JSON into a compact format.
5. Click Copy to copy the processed result.

When the entered content is valid JSON, the extension can format or minify it.

When the content contains a syntax error, the extension displays an error message to help identify the problem. The original content remains available for correction.


The Format function displays JSON using consistent indentation, making objects and arrays easier to read.


The Minify function removes unnecessary spaces, indentation, and line breaks while preserving the JSON structure and values.


JSON Formatter Offline does not collect, store, log, transmit, sell, or share JSON content.

The extension only processes content that the user manually enters or pastes into the popup. It does not automatically inspect network traffic, websites, developer tools, local files, or open tabs.

The extension does not access browsing history, cookies, passwords, personal information, or account data.


The extension does not request access to websites and does not use content scripts, remote code, analytics services, advertising services, or external APIs.

Clipboard access occurs only after the user clicks the Copy button.


All validation, formatting, and minification operations run locally inside Firefox. An Internet connection is not required.