Input
1
Ln 1 Col 1
Indent
Output
// output appears here
—

Jsonic's JSON linter validates your JSON against the JSON specification and reports the exact line and position of every syntax error. Paste any JSON string and click Validate to check it without reformatting. Click Format to fix indentation after correcting errors. All processing happens locally in your browser — your data is never uploaded.

How to lint JSON online

  1. Paste your JSON into the left panel, or upload a .json file.
  2. Click Validate to run the linter and check for syntax errors.
  3. Read the error message — it shows the line, column, and type of error.
  4. Fix the error in the input panel.
  5. Click Validate again to confirm the JSON is now valid.

FAQ

What is JSON linting?

JSON linting is the process of checking a JSON string for syntax errors. A linter parses the JSON and reports any violations of the JSON specification, such as trailing commas, unquoted keys, single quotes, or missing brackets.

What errors does the JSON linter catch?

The linter catches all JSON syntax errors: trailing commas, single-quoted strings, unquoted keys, missing or mismatched brackets, comments, invalid escape sequences, and undefined/NaN values.

What is the difference between JSON lint and JSON validate?

They mean the same thing in the context of syntax checking. "Lint" originated in code quality tools and is commonly used for JSON syntax checking. "Validate" can also mean checking data against a JSON Schema — which is a different, more advanced check.

Is my JSON uploaded when I lint it?

No. The linter runs entirely in your browser using JavaScript. Your JSON is never sent to any server.

Can I lint a JSON file?

Yes. Click Upload and select a .json or .txt file. The linter runs as soon as the file is loaded.

What does "Unexpected token" mean in JSON?

"Unexpected token" means the parser found a character it did not expect at that position. Common causes are a trailing comma (unexpected } or ]), a single quote (unexpected '), or an unquoted key (unexpected identifier).

How do I fix a trailing comma in JSON?

Remove the comma after the last item in the object or array. For example, change {"a":1,"b":2,} to {"a":1,"b":2}. The linter highlights the exact position.

Can I validate JSON against a schema?

This tool checks JSON syntax. For schema validation — verifying that a JSON value matches a defined structure — use the JSON Schema Validator.