Diff Checker API

Compare two texts or JSON documents online and see every change highlighted line by line. Whitespace-insensitive and key-sorted JSON modes. Free and instant.

The Diff Checker is also available as a free REST API. Send a POST request with a JSON body to https://dot.tools/api/tools/diff-checker — no authentication, no API key, CORS enabled. Successful calls return { "ok": true, "result": { … } }; failures return HTTP 400 or 422 with an error body.

Request body

Field	Type	Required	Description
`mode`	"text" \| "json"	required	Compare raw text line-by-line, or parse both sides as JSON first (semantic compare).
`a`	string	required	Original (old) content.
`b`	string	required	Changed (new) content.
`ignoreWhitespace`	boolean	required	Ignore leading/trailing whitespace on each line when comparing (jsdiff ignoreWhitespace semantics).
`sortKeys`	boolean	required	JSON mode only: recursively sort object keys before comparing, so pure key-order differences produce no diff. Arrays keep their order.

Response

Field	Type	Required	Description
`rows`	object[]	required	Per-line diff rows in display order. Empty when error is set.
`stats`	object	required	Diff tallies.
`error`	unknown	required	Error message when the diff could not be computed (JSON parse failure or inputs too different).
`errorSide`	unknown	required	Which input failed JSON parsing, when applicable.
`errorLine`	unknown	required	1-based line of the JSON parse error, when applicable.
`errorColumn`	unknown	required	1-based column of the JSON parse error, when applicable.

Example request

curl -X POST https://dot.tools/api/tools/diff-checker \
  -H 'Content-Type: application/json' \
  -d '{
  "mode": "json",
  "a": "{\n  \"name\": \"dot-api\",\n  \"version\": \"1.2.0\",\n  \"timeout\": 30,\n  \"retries\": 3\n}",
  "b": "{\n  \"name\": \"dot-api\",\n  \"version\": \"1.3.0\",\n  \"timeout\": 60,\n  \"retries\": 3\n}",
  "ignoreWhitespace": false,
  "sortKeys": true
}'

Sample response

{
  "ok": true,
  "result": {
    "rows": [
      {
        "type": "context",
        "text": "{",
        "oldLine": 1,
        "newLine": 1
      },
      {
        "type": "context",
        "text": "  \"name\": \"dot-api\",",
        "oldLine": 2,
        "newLine": 2
      },
      {
        "type": "context",
        "text": "  \"retries\": 3,",
        "oldLine": 3,
        "newLine": 3
      },
      {
        "type": "removed",
        "text": "  \"timeout\": 30,",
        "oldLine": 4,
        "newLine": null
      },
      {
        "type": "removed",
        "text": "  \"version\": \"1.2.0\"",
        "oldLine": 5,
        "newLine": null
      },
      {
        "type": "added",
        "text": "  \"timeout\": 60,",
        "oldLine": null,
        "newLine": 4
      },
      {
        "type": "added",
        "text": "  \"version\": \"1.3.0\"",
        "oldLine": null,
        "newLine": 5
      },
      {
        "type": "context",
        "text": "}",
        "oldLine": 6,
        "newLine": 6
      }
    ],
    "stats": {
      "added": 2,
      "removed": 2,
      "unchanged": 4
    },
    "error": null,
    "errorSide": null,
    "errorLine": null,
    "errorColumn": null
  }
}

Use the free Diff Checker in your browser, read the Diff Checker guide, or import the full OpenAPI specification.