Comments in JSON – Remove Invalid JSON Comments

Standard JSON does not support line or block comments. If comments were copied from JavaScript or a JSON-like configuration file, remove them without touching comment-like text inside quoted strings.

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Common invalid JSON examples

Load one broken syntax pattern at a time, run the repair, and compare the declared rule with the resulting repair log.

Trailing commas

Trailing comma

Remove commas that appear immediately before closing object or array delimiters without touching commas stored inside string values.

{"roles":["admin","editor",],"active":true,}

Review: Confirm that each removed comma was only formatting punctuation and did not represent an intentionally missing value.

JavaScript-style object

Trailing comma · Single-quoted string · Unquoted object key

Convert identifier-like keys and single-quoted strings from a JavaScript object literal into standard JSON syntax.

{
  name: 'VetaTool',
  features: ['repair', 'diff',],
}

Review: Review every inferred key and string boundary because apostrophes and JavaScript escaping can make the intended text ambiguous.

JavaScript comments

JavaScript comment

Remove line and block comments that are legal in some configuration formats but are not allowed by the JSON grammar.

{
  // feature flag
  "enabled": true /* temporary rollout */
}

Review: Check whether a removed comment contained operational context that should be preserved outside the repaired JSON document.

Markdown code fence

Markdown code fence

Strip one outer Markdown fence commonly added around JSON returned by chat assistants, documentation, or copied code blocks.

```json
{"name":"Ada","active":true}
```

Review: Verify that the fence wrapped the entire payload and that no explanatory prose outside the code block was discarded.

Unsupported JavaScript literals

Undefined value · Non-finite number

Replace undefined and non-finite numbers that JavaScript accepts but standard JSON cannot represent with reviewable null placeholders.

{"missing":undefined,"score":NaN,"limit":Infinity}

Review: Decide whether null is the correct business value, or whether the property should be removed or represented another way.

Missing and redundant commas

Missing comma · Redundant comma

Insert a separator between adjacent complete values and remove extra separators only where surrounding tokens identify the boundary.

{"first":1 "second":2,,"third":3}

Review: Confirm that inferred separators match the intended property boundaries and that no omitted value was represented by an empty slot.

Mismatched delimiters

Mismatched delimiter

Replace or add a closing brace or bracket when the nested token stack identifies one bounded structural mismatch.

{"items":[1,2,3}

Review: Inspect the surrounding nesting because heavily damaged objects can have more than one plausible brace or bracket completion.

Escaped JSON string

Escaped JSON string

Decode one outer JSON string layer when a field contains an escaped object or array instead of a directly nested JSON value.

{"payload":"{\"name\":\"Ada\",\"active\":true}"}

Review: Confirm that the field is intended to become a nested object rather than remain a string consumed by another downstream system.

Repair log

Run the repair to see each change and why it was made.

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JSON comment repair

Why standard JSON does not allow comments

Some configuration formats deliberately extend JSON with comments, but JSON.parse follows standard JSON grammar and rejects // and /* */ tokens outside strings. The repair tool removes complete JavaScript-style comments while preserving the surrounding JSON text. This tool is free to use. No account or payment is required.

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What you can do here

  • Browser-local JSON processing
  • Route-specific malformed JSON example
  • Focused parser or repair guidance
  • Broken and corrected JSON example
  • Related JSON problem navigation
  • JavaScript comment removal

Steps

  1. Paste the commented JSON-like text or use the preloaded example.
  2. Run JSON Repair and review the removed line or block comments.
  3. Move important operational notes outside the JSON document before using the cleaned result.

JSONC and JavaScript are not strict JSON

Editors and tools may call a format JSON with comments or JSONC, but a strict JSON parser does not recognize those comments. The consumer and file extension determine whether comments are allowed.

Preserve comment-like text inside strings

Text such as https://example.com or the literal characters /* note */ can be valid string content. A safe comment remover must distinguish quoted text from comment tokens in JSON structure.

JSON comment removal example

A line comment and a block comment appear outside string values.

Commented input

{// profile
"name":"Ada"/* active user */}

Strict JSON

{
"name":"Ada"}

Common questions

Frequently asked questions

Can JSON contain comments?

No. Standard JSON has no line-comment or block-comment syntax.

What is JSONC?

JSONC is a JSON-like format used by some tools that adds comments, but it requires a parser that explicitly supports that extension.

Will removing comments change URLs inside strings?

A correct repair should not. Comment markers that occur inside quoted JSON strings are data and must be preserved.

Recommended next steps

Single Quotes in JSONConvert JavaScript-style single-quoted keys and string values to valid JSON.Unquoted Keys in JSONAdd required double quotes around JavaScript-style object keys.JSON Repair Online – Fix Invalid JSONApply conservative syntax repairs and review every reported change.

Debugging a specific JSON issue? Browse JSON troubleshooting.