What is JSON? Validate it and fix common errors

What JSON is

JSON (JavaScript Object Notation) is a text format used for configuration files, API requests, and data exchange. It is readable, but strict: one missing comma or extra quote can make parsing fail.

Core structure

JSON uses objects, arrays, and primitive values. Objects use braces and keys must be double-quoted; arrays use brackets. Valid values are strings, numbers, booleans, null, objects, and arrays.

{ "user": { "name": "Lin", "active": true }, "tags": ["api", "docs"] }

Common validation failures

• Single quotes or unquoted keys.
• A trailing comma after the final item.
• An unescaped line break or quote inside a string.
• JavaScript-only values such as undefined, comments, or functions.

A useful debugging order

Use a formatter or validator to find the error line, then check matching braces and brackets from the outside in. Once syntax is valid, validate field names, types, and business rules separately.

Takeaway

Syntax validation is the first gate for data quality. Valid JSON does not guarantee useful data, but invalid JSON prevents every later check.