JSON5 vs JSONC: Comments in JSON

Quick answer: Plain JSON has no comments and no trailing commas. JSONC is "JSON with Comments" — it adds // and /* */ comments (and tolerates trailing commas), popularized by VS Code. JSON5 is a larger superset that also allows unquoted keys, single quotes, and more relaxed numbers. Use JSONC for config in tools that already accept it; use JSON5 when you want fully human-friendly config and control the parser. Strip either back to strict JSON with the JSON Trimmer.

JSON (RFC 8259) is a data-interchange format with a deliberately minimal grammar — no comments, no trailing commas, double quotes only, quoted keys. That strictness is a feature for machine-to-machine data, but a pain for hand-edited config files where you'd like to leave a note or reorder lines cleanly. JSONC and JSON5 exist to fill that gap.

JSONC is "JSON plus comments" and little else. JSON5 is a genuinely different, more permissive syntax.

JSONC shines where the tooling already understands it:

{
  // TypeScript compiler options
  "compilerOptions": {
    "strict": true,
    "target": "ES2022", // newest supported
  }
}

VS Code settings, tsconfig.json, and many editor configs accept JSONC. It's the low-friction option: you get comments without a new dependency or a different mental model, and you can drop back to strict JSON by removing the comments.

JSON5 goes further for human-authored files:

{
  unquoted: 'and single quotes',
  trailingComma: true,
  hex: 0xdecaf,
  // and comments
}

Choose JSON5 when configs are complex enough that readability really matters and you're willing to add the json5 parser to your toolchain. The cost is that JSON5 is not JSON — JSON.parse() will reject it, so every consumer needs the JSON5 library.

Both formats are for authoring. The moment data needs to be interchanged, convert to strict JSON:

• Paste a JSONC/JSON5 file into the JSON Trimmer to strip comments, trailing commas, and other extras into spec-compliant JSON.
• Validate the result with the JSON Validator.

If you ever see comments or trailing commas causing JSON.parse() to throw, that's the signal you've got JSONC/JSON5 where strict JSON was expected. For more format trade-offs, see JSON vs YAML and JSON Alternatives.

Can JSON have comments? Not standard JSON. JSONC and JSON5 add comments, but JSON.parse() and strict parsers reject them. Strip comments before interchanging the data.

What's the difference between JSONC and JSON5? JSONC is essentially JSON plus comments (and tolerated trailing commas). JSON5 is a broader superset that also allows unquoted keys, single quotes, and relaxed number formats.

Which should I use for a config file? Use JSONC if your tool already supports it (e.g. VS Code, tsconfig.json) — it's the least friction. Use JSON5 when you want the full set of human-friendly features and can add its parser.

How do I convert JSON5 or JSONC to plain JSON? Remove the comments and trailing commas and quote any bare keys — or paste it into the JSON Trimmer, which outputs strict JSON in one step.