datapry

JSON Validator

Check JSON syntax and see each problem explained with its line and column. Runs in your browser, so nothing is uploaded.

JSON input

Result

Paste JSON to validate it.

Waiting for input

About this tool

A parser's “Unexpected token” message rarely tells you what to fix. This validator explains each problem in plain language, points to the exact line and column, and marks it in the editor. It also warns about valid JSON that can still cause bugs, such as duplicate keys and numbers too large for JavaScript.

How to use it

  1. Paste your JSON or import a file.
  2. Read the result as you type.
  3. Select an issue in the list to jump to it in the editor.

Example

Input
{
  "a": 1,
}
Output
Line 3, column 1: Trailing commas aren't allowed in JSON. Remove the comma before this bracket.

Questions

What does it check beyond syntax?
It warns about duplicate keys, which most parsers resolve by silently keeping the last value, and about numbers JavaScript can't represent exactly, such as 64-bit IDs.
Does it validate against a JSON Schema?
Not yet. This tool checks that the text is well-formed JSON. Schema validation is planned as a separate tool.
Are comments allowed?
No. Standard JSON has no comments, so they're reported as errors. JSON with comments (JSONC) needs them removed first.