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JSON Validator — free, and it runs in your browser

Check whether JSON parses, and see the line and column where it stops.

  • Find out whether JSON parses at all, and precisely where it stops.
  • The error names the line and column, not just "invalid input".
  • Catches the four things that are legal JavaScript and illegal JSON.
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  • 70 tools

    Free, with no account and no watermark

  • 0 bytes

    Of your files or text uploaded — this tool runs in the tab

  • No queue

    The work happens in this tab, not in a line behind other users

Three steps, nothing to install

JSON Validator in three steps

  1. JSON123456Paste it in — it never leaves the tab

    Paste the JSON

    Whatever you were handed — an API response, a config file, a fixture that suddenly stopped working.

  2. JSONEvery field, broken out and checked

    See exactly where it breaks

    A valid document is confirmed as such. An invalid one reports the line and column the parser reached, with its own message.

  3. Copy REPORT

    Fix it in place

    Correct it in the editor. The verdict updates as you type, so you see the moment it parses.

Why use JSON Validator

  • The four usual suspects

    Trailing commas, single quotes, unquoted keys and comments are all valid JavaScript and none are valid JSON. That gap is where almost every failure comes from.

  • Errors that say where

    When something will not parse you get the line and column it gave up on, not a red box that says the input was invalid.

  • Your text stays in the page

    What you paste is not transmitted or stored, so an API response full of customer records, a token or an internal query never leaves your machine.

Frequently asked questions

Because the JSON specification does not allow one. JavaScript object literals do, which is why this is the single most common JSON mistake — the syntax looks identical but the rules differ.

What makes JSON invalid

JSON is a deliberately small format, and almost every error comes from one of a handful of causes. In rough order of frequency: a trailing comma after the last item, single quotes instead of double, unquoted keys, a missing closing brace or bracket, and an unescaped character inside a string.

The overlap with JavaScript is what makes these easy to write. Every one of the first three is legal in a JavaScript object literal. JSON borrowed the syntax but not the leniency.

Reading the error position

A parser reports where it could no longer continue, which is not necessarily where you made the mistake. Forget a closing brace on line 4 of a 400-line document and the error appears on line 400 — that is simply where the input ran out. When the reported position looks wrong, work backwards from it looking for something left unclosed.

Strictly speaking

Valid JSON does not mean correct data. This checks syntax only — that the document parses. Whether it has the fields your API expects is a separate question that needs a schema.

Once it parses, the JSON formatter pretty-prints or minifies it. To convert it, see JSON to CSV and JSON to XML. For YAML, use the YAML validator.

Often used alongside

  • JSON Formatter

    Pretty-print JSON with the indentation you choose, or minify it.

  • YAML Validator

    Validate YAML syntax and preview the parsed result as JSON.

  • JSON to CSV

    Flatten a JSON array of objects into CSV rows.

  • JSON to XML

    Convert JSON structures into equivalent XML markup.

  • XML Beautifier

    Format, minify and check XML without mangling CDATA or attributes.

  • XML to JSON

    Convert XML documents into readable JSON.

Related guides

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