JSON File Viewer Online: Open and Read .json Files Privately

How to open a JSON file

Press Open and pick a .json file, or drag the file onto the editor.
Read the structure in the Tree tab, or switch to Formatted for indented text.
Use Download to save a formatted or minified copy.

Opening files without uploading them

The file is read with your browser's file API and handed to the same in-page engine used for pasted text. There is no upload step, no server and no copy of your data kept anywhere else, which is what you want for exports, backups and configuration files.

Files that will not open

If the file is not valid JSON the status bar shows the error with its line and column. Common causes are a byte-order mark, trailing commas, comments, or several JSON documents in one file (JSON Lines). Use Fix JSON for the first three; for JSON Lines, paste a single line at a time.

What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based data format that is easy for people to read and for machines to parse. It is the de facto standard for web APIs, configuration files and data exchange between services. A JSON document is built from just six value types: objects, arrays, strings, numbers, booleans and null.

{
  "name": "Ada",
  "age": 36,
  "admin": true,
  "skills": ["math", "code"],
  "address": { "city": "London" },
  "manager": null
}

JSON is stricter than JavaScript object literals: keys and strings must use double quotes, trailing commas are not allowed and comments are not part of the specification (RFC 8259).

Why format JSON?

APIs usually return minified JSON on a single line, which is efficient for machines but unreadable for people. Formatting (also called pretty printing or beautifying) adds consistent indentation and line breaks so that you can scan the structure, spot mistakes and review changes. Minifying does the opposite and strips whitespace to reduce size.

Frequently asked questions

Which file types are supported?

Any text file that contains valid JSON, usually .json. Plain .txt files work too.

Is my JSON uploaded to a server?

No. Parsing, validation, formatting, diffing and code generation all run inside your browser, using a Web Worker. Your data is never sent to any server, which makes the tool safe for API responses, configuration files and other sensitive payloads.

Does it work offline?

Yes, after the first visit. The editor and tools are stored in your browser, so you can use them without a connection. Only the TypeScript, CSS and HTML language workers used for extra highlighting in the Code tab are downloaded the first time you use them.

How large a JSON file can I open?

Files of 20 MB and more work. Parsing happens off the main thread and the tree view is virtualized, so only the rows you can see are rendered. The editor switches to a lighter mode for very large documents.

What is the difference between formatting and minifying JSON?

Formatting (pretty printing) adds line breaks and indentation so people can read the data. Minifying removes all optional whitespace to make the payload as small as possible for network transfer or storage. Both produce identical data.

JSON File Viewer