JSONC to JSON Converter

JSONC in one paragraph

JSONC (“JSON with Comments”) is ordinary JSON plus two conveniences: // line comments and /* … */ block comments, and a trailing comma after the last item of an object or array. Microsoft introduced it for VS Code’s settings.json and launch.json, and it is now used by tsconfig.json, jsconfig.json, devcontainer.json, .eslintrc.json, Deno’s deno.jsonc, Biome and Turborepo. Strict JSON readers, from JSON.parse to Python’s json module and jq, reject both conveniences, so a config that works in your editor can fail in a script or a CI step.

What the converter changes, and what it does not

Only the two JSONC additions are touched. Comments are removed wherever they appear, including between a key and its value; text that merely looks like a comment inside a string, such as "https://example.com/*" or a glob like "**/*.ts", is left alone. A comma is removed when the next meaningful character is } or ], even if a comment sits in between.

Everything else is passed through exactly: key order, duplicate keys, string escapes and number spellings, so 1.50, 1e3 and 64-bit integers are not rewritten. The result is pretty-printed with the indent you choose in the toolbar, and Sort keys works too. An info note reports how many comments and trailing commas were removed, so you can tell at a glance whether the file was already strict.

Errors point at your original lines

Comments are blanked out in place rather than deleted, so every character keeps its position. When the remaining text is not valid JSON, the error shows the line and column in the file you pasted, not in some intermediate version. A missing comma between two settings, an unclosed /*, or a stray character are all reported where they are.

JSONC deliberately stops at comments and trailing commas. Unquoted keys, single-quoted strings, hexadecimal numbers, Infinity and NaN belong to JSON5; when the converter meets them it says so and points you to the JSON5 to JSON converter. Keeping the two apart means a typo in a tsconfig is reported as a mistake instead of being quietly accepted.

Typical uses

• Read a value from tsconfig.json in a shell script: convert, then pipe the strict JSON into jq '.compilerOptions.paths'.
• Merge editor settings from several machines with a JSON diff tool that does not understand comments.
• Send a Dev Container or VS Code configuration to an API or store it in a database column that validates JSON.
• Check a hand-edited config before committing: if it converts, the structure is sound.

The comments are gone in the output, so treat the JSONC file as the source and regenerate the strict copy when it changes. To tidy a JSONC file while keeping its comments, use the JSON5 / JSONC formatter instead; background on the dialects is in the guide to JSON with comments.

Examples

{
  "compilerOptions": {
    "target": "ES2023",
    "module": "NodeNext",
    // Keep these in sync with eslint
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "paths": {
      "@app/*": ["./src/*"], /* path alias */
    },
  },
  "exclude": ["dist", "**/*.spec.ts",],
}

{
  "compilerOptions": {
    "target": "ES2023",
    "module": "NodeNext",
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "paths": {
      "@app/*": [
        "./src/*"
      ]
    }
  },
  "exclude": [
    "dist",
    "**/*.spec.ts"
  ]
}

// Dev Container for the API service
{
  "name": "api",
  "image": "mcr.microsoft.com/devcontainers/typescript-node:22",
  "forwardPorts": [3000, 9229],
  "customizations": {
    "vscode": {
      "extensions": [
        "dbaeumer.vscode-eslint", // linting
        "esbenp.prettier-vscode",
      ],
    },
  },
  "postCreateCommand": "npm ci",
}

{
  "name": "api",
  "image": "mcr.microsoft.com/devcontainers/typescript-node:22",
  "forwardPorts": [
    3000,
    9229
  ],
  "customizations": {
    "vscode": {
      "extensions": [
        "dbaeumer.vscode-eslint",
        "esbenp.prettier-vscode"
      ]
    }
  },
  "postCreateCommand": "npm ci"
}

Common errors and how to fix them

Related tools

• JSON5 to JSON
• JSON5 / JSONC formatter
• JSON formatter
• json validator
• json with comments
• json comments not allowed
• json trailing comma