Data tool

JSON Corruptor

Break JSON on purpose to test validators, API clients, importers, error handling, and messy-data cleanup flows.

Runs Locally

This tool runs in your browser. Files never leave your device.

JSON input

Drop a JSON/TXT file here or paste JSON below.

Open file

Drag and drop a .json or .txt file anywhere inside this input card.

Lines

Objects

Arrays

Keys

Corrupted output

468 B output · invalid JSON

Damage presetSeed

Output validation

Expected property name or '}' in JSON at position 31 (line 5 column 1)

{
  "users": [
    null,
    {
// generated bad comment 584
      "iid": 1002,
      "iid_duplicate": 1002,
      "name": "Jane Doe",
// generated bad comment 966
      email: "jane@example.com",
      "plAn": "Free",
      "active": false,
      "credits": 18,
      "tags": [
        false,
        false
      ],
      "createdAt": "2026-06-03T11:15:00Z
    }
  ],
// generated bad comment 290
  "eta": {
    "page": 1,
    "hasMMore": false,
    "source": true,}
}

Damage controls

Use custom sliders when you need a specific kind of broken JSON.

Remove commas7%Add trailing commas10%Break quotes6%Unquote keys8%Mutate keys/values12%Blank values8%Duplicate keys7%Swap value types10%Insert comments8%Truncate output3%Insert junk text5%

What this tool does

JSON Corruptor takes valid JSON and breaks it in controlled ways, dropping brackets, mangling quotes, and injecting noise, so you can test how your code handles bad input. It is built for hardening parsers and error handling against the malformed JSON that shows up in the real world.

How it works

Paste valid JSON, choose how to corrupt it, and the tool generates broken versions in your browser. Copy the output to feed into your tests. Nothing is uploaded.

When to use JSON Corruptor

Testing a parser's error handling

Hardening an API against malformed payloads

Building negative test cases for JSON input

Checking how a UI handles a bad response

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