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JSON Validator

Check whether a JSON document is valid. Errors are reported with line and column, plus a plain-English explanation of the likely cause.

Runs in your browser — files never leave your device

Free · No sign-upOutputs Validation report
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How to use JSON Validator

  1. Paste the JSON to check.

  2. Click Validate.

  3. If invalid, jump to the reported line and column and fix the highlighted cause.

  4. Re-validate until the green summary appears.

About this tool

"Unexpected token" errors in production often trace back to hand-edited JSON. This validator uses the strict native parser and translates its errors into actionable messages — pointing at the line and column and naming the usual suspects: trailing commas, single quotes instead of double, unquoted keys, comments (JSON has none), and unescaped control characters in strings. Valid documents get a summary of their structure (type, key count, nesting depth).

This is often the fastest way to track down why a config file or API payload is silently failing to parse somewhere in a larger system — pinpointing the exact line and likely cause instead of scanning the whole document by eye.

Common ways people use this

  • Tracking down why a hand-edited config file is failing to load in an application
  • Verifying a JSON payload is well-formed before sending it to an API
  • Checking JSON pasted from a support ticket or bug report before investigating further

Tips for better results

  • If you're not sure why JSON copied from another source is failing, check first for smart/curly quotes (“ ”) accidentally introduced by a word processor — they look like regular quotes but aren't valid in JSON.
  • Use the structure summary shown for valid documents as a quick sanity check that the data has the shape you expect (e.g. an array with the right number of items).

Frequently asked questions

Why is JSON with comments invalid?
The JSON specification has no comment syntax. Some tools accept them anyway (JSONC), but strict parsers — including the ones in browsers and most languages — reject them.
Are single quotes really not allowed?
Correct. JSON strings and keys must use double quotes. Single quotes are a JavaScript habit that strict JSON parsers reject.
The validator says valid but my API rejects the JSON — why?
The syntax is valid, but the API likely expects a particular schema: specific keys, types or value ranges. Check the API's documentation for its required structure.
What does the structure summary tell me?
For valid JSON, it reports the root type (object or array), the number of keys or items, and how deeply the structure is nested — a quick way to sanity-check the shape of the data.
Can I validate JSON copied from a Python or JavaScript file?
Only the JSON portion itself — if you copy a JavaScript object literal that uses single quotes or unquoted keys, it needs to be converted to strict JSON syntax first before it will validate.

Related tools

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