What is a JSON file?

You downloaded your data from an app, a game asked you to replace a settings file, or someone sent you something called export.json. Here’s what that file is, in plain English, and how to look inside it.

Written by the developer of Sonnet · Published 13 September 2026

Short answer

A JSON file (.json) is a plain text file that stores data as names and values, like "name": "Ava", grouped into objects and lists. Apps and websites use it to save settings, exchange data and hand you exports of your account. It isn’t a program and can’t run anything, so opening it is safe, though it may contain private data. To read it comfortably, open it in a JSON viewer. Any text editor also works.

Get Sonnet free A JSON viewer for Android, offline.

What a JSON file looks like

JSON stands for JavaScript Object Notation. It started in web development and is now used almost everywhere. A small example:

{
    "name": "Ava Thompson",
    "age": 34,
    "premium": true,
    "languages": ["English", "Portuguese"],
    "address": {
        "city": "Lisbon",
        "country": "PT"
    },
    "lastOrder": null
}

Read it line by line: this person’s name is Ava Thompson, age 34, has premium, speaks two languages, lives in Lisbon, and has no last order. Every JSON file is built from the same six kinds of value:

Text (a string) in double quotes: "Lisbon"
Numbers: 34, 19.99
True or false: true, false
Nothing: null
Lists (arrays) in square brackets: ["English", "Portuguese"]
Groups of named values (objects) in curly braces, like the address above

Objects and lists can sit inside each other as deeply as needed. That nesting is why a large JSON file is hard to read as raw text, and why JSON viewers show it as a tree you can fold and unfold.

Where JSON files come from

Data downloads. When you ask Instagram, Facebook, Discord, Google Takeout and many others for a copy of your data, most of it arrives as JSON files in a zip. See our guides to Instagram and Discord downloads.
App and game settings. Many apps, games, mods and emulators store their configuration as JSON because it’s easy to read and edit.
Backups and exports. Note apps, password managers, habit trackers and budgeting apps often export to JSON.
Websites and APIs. When an app talks to a server, the data travelling back and forth is very often JSON. Developers see it constantly.
Maps. .geojson files are JSON that describes places and shapes.

Is it safe to open a JSON file?

Opening one, yes. A JSON file is just text. It contains no code that runs when you view it, the same way reading a .txt file can’t install anything. Two sensible cautions:

Check the real extension. A file named data.json.exe or data.json.apk is not a JSON file. Don’t run it.
Mind what’s inside. JSON files often hold personal data, passwords or access tokens. Think before uploading one to a website or sending it on.

How to open a JSON file

On Android

Android has no built-in app for JSON. Install a JSON viewer, then tap the file and choose it under Open with. Our app, Sonnet, shows the file as a foldable tree, lets you edit values, and works offline. For other options, see how to open a JSON file on Android. For chat and email attachments, see this guide.

On Windows

Right-click → Open with → Notepad shows the text. Most web browsers also display a JSON file you drag into them, and Firefox formats it as a collapsible tree.

On a Mac

Open it with TextEdit, or drag it into a browser window.

JSON compared with similar formats

Format	Looks like	Best for
JSON `.json`	Nested names and values	Structured data with groups and lists
CSV `.csv`	Rows and columns separated by commas	Flat tables; opens in any spreadsheet
XML `.xml`	Tags like `<name>Ava</name>`	Older systems and documents; more verbose
JSON Lines `.jsonl`	One JSON object per line	Logs and very large exports
JSONC	JSON plus `//` comments	Config files for developer tools

JSON Lines and JSONC look almost identical to JSON, but strict JSON tools reject them. If a file “looks like JSON” and still won’t open, that’s a likely reason. See Invalid JSON: what the error means.

See inside any JSON file

Sonnet opens JSON files on Android as a clean, collapsible tree, and lets you edit them with a tap. Offline, no ads, no account. Free on Google Play.