Skip to main content
FetchToolKit logoFetchToolKitFetchToolKit

JSON Validator

Check if your JSON is valid, pinpoint the exact line and column of any syntax mistake, and fix trailing commas or comments in one click.

Free to useNo sign-up requiredWorks in your browserPrivacy focused

JSON Validator Workspace

How to use

  1. 1

    Step 1

    Paste your JSON or configuration snippet into the Input JSON box, or click Load JSONC Sample to test an example with errors.

  2. 2

    Step 2

    Check the status banner to see if the JSON is valid or view the exact Line and Column number where an error occurred.

  3. 3

    Step 3

    If your file has comments or trailing commas, click Auto-Fix Comments & Trailing Commas to clean it into valid JSON.

Key features

  • Pinpoints the exact line and column number of syntax errors with a clear visual pointer (^)
  • Shows the broken line of code so you can spot missing quotes, colons, or brackets right away
  • One-click Auto-Fix removes // and /* */ comments and trailing commas without altering URLs inside strings
  • Validates large JSON files up to 10 MB privately in your browser

Supported formats

JSON

File limits & notes

Validates JSON data up to 10 MB in your browser. Auto-Fix automatically removes comments and trailing commas before closing brackets; other syntax errors like missing colons or unquoted keys are highlighted by line and column so you can fix them quickly.

Frequently asked questions

View all FAQs
What issues can Auto-Fix repair automatically?

Auto-Fix removes single-line (//) and multi-line (/* */) comments as well as trailing commas before closing braces (}) or brackets (]), while leaving URLs like 'https://...' inside quotes untouched.

Why are trailing commas and single quotes marked as errors in JSON?

Standard JSON requires double quotes around all property names and strings and does not allow a comma after the last item in an object or array.

Is it safe to validate private configuration files here?

Yes. Your JSON is checked entirely inside your browser and is never uploaded or logged anywhere.

Practical Example: Cleaning Up a Configuration File with Comments and Trailing Commas

Sample Input
A project configuration snippet containing // comments and trailing commas that fails in strict JSON parsers.
Result
Highlights the exact lines with comments and trailing commas and repairs the file into valid JSON in one click.