JSON with comments: working with JSONC files

Strict JSON versus JSONC

Use strict JSON when you are exchanging data with an API or another system that expects the JSON standard. Use JSONC when the file is a human-maintained configuration and the receiving tool explicitly supports comments.

JSONC comments are source annotations. They can help explain a setting, but they are not values in the data model. If you later hand the file to a strict JSON consumer, comments must be removed or the handoff must use a verified strict output.

{
  // Local development endpoint.
  "endpoint": "https://api.example.test/v1//status",
  "retry": {
    "attempts": 3,
    /* Keep this low for browser tests. */
    "backoffMs": 250,
  }
}

• Open local JSON and JSONC files

Avoid regex cleanup

The URL in the fixture contains // inside a string. That is not a comment. A simple regular expression that removes everything after // can corrupt valid data.

A real parser has to know whether it is inside a string, a line comment, a block comment, an object, or an array. This is also why a trailing comma in a JSONC object can be acceptable to a JSONC parser while still invalid in strict JSON.

Unsafe cleanup idea: remove //.* from every line.

Open and search comments deliberately

Open the .jsonc file in JSON All-in-One, confirm it is treated as JSONC, then inspect both the structured data and the comment text. Comment search is useful for configuration audits: search for TODO, deprecated, production, or a feature flag name.

Keep the inspection focused: the useful view is the comment and the associated setting together, not a whole desktop squeezed into an unreadable image.

Prepare strict JSON handoff carefully

When another system expects strict JSON, produce and inspect a cleaned result through a verified workflow. The expected strict form of the sample removes comments and trailing commas but keeps string values such as the endpoint URL unchanged.

Syntax normalization and schema validation are different tasks. If you need a starting schema, use Generate JSON Schema from sample JSON.

{
  "endpoint": "https://api.example.test/v1//status",
  "retry": {
    "attempts": 3,
    "backoffMs": 250
  }
}

• Generate a schema after cleanup

JSONC is not JSON5

Some tools use JSON5 features such as additional number spellings or object key relaxations. Comments working in one file does not mean every JSON5 feature is accepted in another.

JSON All-in-One also has NDJSONC support for line-delimited relaxed records, but NDJSONC is separate from ordinary JSON Lines. For record streams, read How to open JSONL and NDJSON files.

Troubleshooting

• If strict JSON tools reject the file, check for comments and trailing commas first.
• If search misses a comment, confirm comments are included in the search scope.
• If a // appears inside a string, keep it as data.
• If a downstream API rejects cleaned output, inspect the exact bytes you saved rather than assuming comments were the only issue.