JSON vs JSON5 vs JSONC: What's the Difference?

JSON has spawned relaxed variants that fix its biggest annoyances for human-edited files. The three you'll meet are plain JSON, JSONC, and JSON5.

Plain JSON

The strict standard. No comments, no trailing commas, double-quoted keys and strings only. Universally supported. Use it for data interchange and anything a machine reads or writes.

JSONC (JSON with Comments)

JSON plus // and block comments — essentially the only addition. Popularized by VS Code for settings.json and tsconfig.json:

{
  // a single-line comment
  "port": 8080
}

Use it for config files in tools that explicitly support it. Plain parsers reject it.

JSON5

The most relaxed. Adds comments, trailing commas, unquoted keys, single quotes, and more:

{
  port: 8080,        // unquoted key, comment
  host: 'localhost', // single quotes
  tags: ['a', 'b',], // trailing comma
}

Use it for human-authored config where you control the parser.

Comparison

Feature	JSON	JSONC	JSON5
Comments	No	Yes	Yes
Trailing commas	No	No	Yes
Unquoted keys	No	No	Yes
Single quotes	No	No	Yes
Universal parser support	Yes	No	No

Which should you use?

• Sending or storing data? Plain JSON.
• Config in a tool that supports comments? JSONC.
• Hand-writing rich config you control? JSON5.
• Want comments and clean nesting without a JS superset? Consider YAML or TOML.

Convert to strict JSON

Need a relaxed file turned into portable JSON? Paste it into the validator to spot the non-standard bits, then clean and format it with the formatter.