JSON syntax error guide

Comments Are Not Allowed in JSON: What It Means and How to Fix It

The JSON standard has no comment syntax. JavaScript-style // comments and /* block comments */ make a document invalid for strict JSON parsers.

What this JSON error means

Typical parser message

SyntaxError at / when JSON contains a comment

Remove comments for portable JSON. If comments are a real product requirement, use a format that explicitly supports them rather than depending on a permissive parser.

Broken JSON vs. corrected JSON

Compare the invalid syntax with a corrected version before applying the same change to your payload.

Invalid JSON

{
  // primary user
  "name":"Ada"
}

Valid JSON

{
  "name":"Ada"
}

Common causes of this JSON error

●Treating JSON like a JavaScript configuration file
●Copying JSONC from tools such as VS Code settings
●Adding inline documentation to API payloads
●Using a permissive parser locally while production uses a strict parser

Fix and validate your JSON

After correcting the suspected syntax, run the complete payload through a validator. If it still fails, use the diagnostic tool to locate the next parser error before formatting the final JSON.

Check JSON for errors Fix invalid JSON JSON Validator JSON Formatter

Related JSON errors

JSON Unexpected Token Error

Understand and fix JSON unexpected token errors. See broken and corrected examples, common causes, and a fast workflow for finding the exact invalid character.

Unexpected End of JSON Input

Fix “Unexpected end of JSON input” errors caused by truncated JSON, missing braces or brackets, incomplete strings, and empty API responses.

Trailing Comma in JSON

Learn why trailing commas are invalid in standard JSON and fix objects or arrays copied from JavaScript, TypeScript, JSON5, or configuration files.

Single Quotes in JSON

Fix invalid JSON that uses single quotes. JSON requires double quotes around property names and string values.

JSON Property Names Must Be Double-Quoted

Fix JSON with unquoted object keys. Standard JSON requires every property name to be enclosed in double quotes.

Invalid Escape Character in JSON

Fix invalid JSON escape sequences in Windows paths, regex strings, copied text, and backslash-heavy values.

JSON error FAQ

What does Comments Are Not Allowed in JSON mean?

The JSON standard has no comment syntax. JavaScript-style // comments and /* block comments */ make a document invalid for strict JSON parsers.

How do I fix Comments Are Not Allowed in JSON?

Remove comments for portable JSON. If comments are a real product requirement, use a format that explicitly supports them rather than depending on a permissive parser.