Why will my JSON not validate?

A JSON document fails validation when its syntax breaks the JSON grammar. Common causes include single quotes, an unquoted property name, a missing comma, a trailing comma, comments, or mismatched braces and brackets. Start with the first reported error and inspect the preceding line too.

Valid JSON is not the same as valid application data. A document can parse successfully and still contain the wrong field names, data types, or values for the system that receives it.

Object property names and string values must use double quotation marks. For example, {"name": "Ada", "active": true} is valid JSON. Single quotes and typographic “smart quotes” cannot replace the straight double quotes used as delimiters.

A double quote inside a string needs escaping with a backslash. Backslashes themselves also need escaping. When copying a Windows file path or text from a document editor, check these characters carefully. A raw line break cannot appear inside a JSON string; use an escaped newline sequence instead.

Use commas between object properties and between array items. Do not put a comma after the last property or item. For example, [1, 2, 3] is valid, while [1, 2, 3,] is not.

Curly braces enclose objects, and square brackets enclose arrays. Every opening bracket needs the corresponding closing bracket. If the validator points to a closing brace, the real issue may be a missing value, extra comma, or unmatched bracket earlier in the document.

JSON is a data format, not a JavaScript program. Comments, undefined, functions, NaN, and Infinity are not JSON values. Use strings, numbers, objects, arrays, true, false, or null, as appropriate for the receiving system.

Write booleans and null in lowercase without quotes. The string "false" is different from the boolean false. Numbers cannot have leading zeroes such as 007; use a string if the zeroes are part of an identifier. Duplicate object keys may parse, but different consumers can handle them differently, so remove ambiguity before sending the data.

Formatting makes JSON easier to read; it does not prove that the data is complete or correct. Confirm required fields, units, date conventions, and whether a field should contain a number or a string. Be especially careful with long numeric identifiers, which some software cannot represent exactly as numbers.

If the source is a spreadsheet or CSV file, use the CSV–JSON converter below instead of manually adding quotes and commas to every row. After conversion, inspect empty cells, column names, and representative records before importing the result.