JSON Basics: What Every Beginner Coder Should Know

By the Toolbench team · Updated September 2026

JSON, short for JavaScript Object Notation, is one of the first data formats most beginner programmers encounter, usually while working with an API or a configuration file. It looks intimidating at first glance but follows only a handful of rules.

The core building blocks

JSON is built from just a few types: objects (key-value pairs wrapped in curly braces), arrays (ordered lists wrapped in square brackets), strings, numbers, booleans, and null. Everything in JSON is some combination of these few pieces, nested as deeply as needed.

Why JSON became so common

Before JSON was widespread, data exchanged between systems often used more verbose formats like XML. JSON offered a lighter, easier-to-read alternative that maps naturally onto data structures already common in most programming languages, which is a large part of why it spread so widely.

Common beginner mistakes

Trailing commas after the last item in an object or array are not allowed in strict JSON, unlike in JavaScript object literals. Keys must be wrapped in double quotes, not single quotes. Comments are not permitted anywhere in standard JSON, which surprises people coming from languages that allow them everywhere.

Why validation matters

A single misplaced comma or missing bracket can make an entire JSON file fail to parse, often with an error message that points to the wrong location. Running JSON through a formatter or validator before using it catches these issues immediately, rather than debugging a cryptic parser error deep inside an application.

Format and validate your own

The JSON Formatter and Validator checks JSON for errors and neatly indents it, which also makes nested structures far easier to read at a glance.