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JSON Validator

In-browser only RFC 8259 JSON parser
Result
The result appears here once you enter JSON.
Runs entirely in your browser with the built-in JSON parser.
Related tools View all

Overview

Format, validate, minify, and lint JSON in your browser

Check whether your JSON is syntactically correct. Get a clear valid/invalid verdict with the exact line and column of any error.

  • Format, validate, minify, and lint from one panel
  • Exact line and column for every syntax error
  • 2-space, 4-space, or tab indentation
  • Catches duplicate keys, trailing commas, and comments
  • Runs entirely in your browser
  • All processing runs entirely in your browser
  • Your JSON data is never uploaded to any server
  • Nothing is stored — the page holds no state between sessions
  • No account or login required to use any feature
  • Inspect the network tab to confirm zero outbound requests
  • Confirm a payload parses before using it
  • Jump to the line and column of the first error
  • Pre-flight a pasted API response
  • Check a config file is valid JSON
  • Catch a syntax slip before deploy

Guide

How to use

  1. 1
    Paste your JSON

    Type, paste, or use the Paste button to pull JSON from your clipboard. The Sample button loads a small example to try.

  2. 2
    Choose an action

    Switch between Format, Validate, Minify, and Lint using the tabs. The same input is reused — no need to paste again.

  3. 3
    Read the result

    Formatted and minified output appears in the result pane; validation shows a clear verdict; lint lists every issue with its location.

  4. 4
    Copy or download

    Use Copy to send the result to your clipboard. On the Format and Minify tabs you can also Download the result as a .json file.

Reference

What JSON Lint checks

JSON lint issues and what they mean
IssueWhat it means
Duplicate keyTwo properties in one object share a key — parsers keep only one value.
Trailing commaA comma before a closing bracket or brace — not allowed in strict JSON.
Comment// or /* */ comments — valid in JSON5/JSONC but rejected by JSON.
Single-quoted stringStrings or keys in single quotes — JSON requires double quotes.
Unquoted keyAn object key without quotes — JSON requires every key to be double-quoted.
Byte-order markA hidden BOM character at the start of the input that can confuse parsers.

Pitfalls

Common JSON mistakes

  • Trailing commas

    A comma after the last item in an array or object is fine in JavaScript but invalid in JSON. Remove the comma before the closing bracket or brace.

  • Single quotes

    JSON requires double quotes for every string and key. Single quotes are a JavaScript habit — the Lint tab flags each one so you can swap them.

  • Unquoted keys

    JavaScript object literals allow bare keys like {name: "x"}, but JSON needs {"name": "x"}. Every key must be wrapped in double quotes.

  • Comments

    JSON has no comment syntax. // and /* */ comments are valid in JSON5 and JSONC but a standard parser will reject them — strip them before parsing.

Frequently asked questions

What does "Unexpected token" mean?
It means the parser found a character that does not belong at that position. Common causes are trailing commas, single quotes instead of double quotes, unquoted keys, or comments. The validator reports the exact line and column so you can jump straight to it.
What is the difference between Validate and Lint?
Validate answers one question — is this valid JSON? — and reports the first syntax error. Lint goes further and flags issues a parser tolerates or that only matter in practice, such as duplicate keys.
Does it validate against a JSON Schema?
No. This tool checks JSON syntax, not structure. Schema validation — confirming values match a schema definition — is a separate concern from syntax checking.
Is my JSON sent to a server?
No. Validation runs entirely in your browser. Your JSON never leaves your device.