Files and data

What is JSON?

Short for JavaScript Object Notation.

JSON is a text format for storing structured data as objects, arrays and simple values, widely used by websites and apps to exchange data.

By Utility Mule editorial team Last reviewed September 29, 2026 How we write guides

How it works

JSON describes data using a handful of building blocks: objects of named properties in curly braces, ordered arrays in square brackets, and values that are strings, numbers, true, false or null. Those blocks nest, so one file can describe an order with its customer, delivery address and a list of items.

The format is strict. Property names and strings use double quotes, there are no comments, and a trailing comma after the last item makes the whole file invalid. Numbers, booleans and null have distinct meanings, which matters when converting data: the text “true” isn’t the same as the value true.

JSON vs CSV

CSV is a flat table: every row has the same columns. JSON can represent nested structures that don’t fit neatly into a spreadsheet, such as an order containing several items. Converting JSON to CSV works well for a list of similar flat records; deeper structures need to be flattened into columns such as address.city or split into several tables.

A practical example

The object {"name":"Alex","active":true} has a text value and a boolean value. An array can hold a list of objects like this, one per customer or order.

What to watch out for

Converting nested JSON to a flat CSV table requires choices about arrays and child objects. Formatting JSON improves readability but doesn’t validate its business meaning.

Tools you can use

JSON Formatter · Validate, format and see exactly what is wrong
JSON to CSV · Objects to rows that open in Excel
CSV to JSON · Rows to objects, quoted fields handled

Go a little deeper

Common questions

Why is my JSON invalid?

The usual causes are a trailing comma after the last item, single quotes instead of double quotes, comments, or an unquoted property name. A formatter points to the exact line.

How do I open a JSON file?

Any text editor opens it, and browsers display it with folding. A JSON formatter indents it so the structure is readable, and a converter turns a list of records into a spreadsheet.

Can JSON store dates?

Not as a separate type. Dates are usually stored as text in the ISO format, such as 2026-09-29T10:00:00Z, and the program reading the file converts them.