Compare two texts

Compares before with after using jsdiff (Myers' O(ND) algorithm). changes is the full sequence of added, removed and unchanged pieces at the chosen granularity; concatenating the unchanged and removed values gives before, unchanged and added gives after (when ignoring whitespace or case, unchanged pieces are taken from after). unified and hunks are always a line-level unified diff (GNU diff -u format) with context lines, whatever the mode. identical is true when no differences remain under the chosen options; exact_match compares the raw strings. Limits: 200,000 characters per text; at most 5000 differing lines, or 2000 differing words or characters.

Browser version (runs locally): Text Diff.

Parameters

Also accepted on every endpoint: format (json | text). Parameters may come from the query string, a JSON object body, an urlencoded or multipart form, or (for input) a text/plain body.

Response 200 application/json

Text output (format=text, text/plain): The unified diff (empty when identical).

Errors

Errors are JSON: {"error": "<message>", "code": "<code>", "param": "<name>"?}.

Behaviour

• Idempotent: the same arguments always return the same result.
• Requires a client ID and secret (authentication). Each call is recorded as one metadata row against your client ID; inputs and outputs are never stored or logged. Responses carry cache-control: no-store.
• CORS: any origin may call this endpoint from a browser, using your credentials.

Examples

Responses below were produced by running each request through this code at build time. Long strings are shortened.

curl -X POST 'https://util.caruana.me/api/diff' \
  -H 'content-type: application/json' \
  -d '{"before":"alpha\nbeta\ngamma\n","after":"alpha\nBETA\ngamma\ndelta\n","from_label":"a/notes.txt","to_label":"b/notes.txt"}'

{
  "identical": false,
  "exact_match": false,
  "mode": "lines",
  "unit": "line",
  "options": {
    "ignore_whitespace": false,
    "ignore_case": false,
    "context": 3,
    "from_label": "a/notes.txt",
    "to_label": "b/notes.txt"
  },
  "stats": {
    "added": 2,
    "removed": 1,
    "unchanged": 2,
    "change_blocks": 2,
    "lines_added": 2,
    "lines_removed": 1,
    "chars_added": 11,
    "chars_removed": 5
  },
  "changes": [
    {
      "type": "unchanged",
      "value": "alpha\n",
      "count": 1
    },
    {
      "type": "removed",
      "value": "beta\n",
      "count": 1
    },
    {
      "type": "added",
      "value": "BETA\n",
      "count": 1
    },
    {
      "type": "unchanged",
      "value": "gamma\n",
      "count": 1
    },
    {
      "type": "added",
      "value": "delta\n",
      "count": 1
    }
  ],
  "hunks": [
    {
      "header": "@@ -1,3 +1,4 @@",
      "before_start": 1,
      "before_lines": 3,
      "after_start": 1,
      "after_lines": 4,
      "lines": [
        " alpha",
        "-beta",
        "+BETA",
        " gamma",
        "+delta"
      ]
    }
  ],
  "unified": "--- a/notes.txt\n+++ b/notes.txt\n@@ -1,3 +1,4 @@\n alpha\n-beta\n+BETA\n gamma\n+delta\n"
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "text_diff",
    "arguments": {
      "before": "alpha\nbeta\ngamma\n",
      "after": "alpha\nBETA\ngamma\ndelta\n",
      "from_label": "a/notes.txt",
      "to_label": "b/notes.txt"
    }
  }
}

curl 'https://util.caruana.me/api/diff?before=The%20quick%20brown%20fox&after=the%20quick%20red%20fox&mode=words&ignore_case=true'

{
  "identical": false,
  "exact_match": false,
  "mode": "words",
  "unit": "word",
  "options": {
    "ignore_whitespace": false,
    "ignore_case": true,
    "context": 3,
    "from_label": "before",
    "to_label": "after"
  },
  "stats": {
    "added": 1,
    "removed": 1,
    "unchanged": 3,
    "change_blocks": 1,
    "lines_added": 1,
    "lines_removed": 1,
    "chars_added": 3,
    "chars_removed": 5
  },
  "changes": [
    {
      "type": "unchanged",
      "value": "the quick ",
      "count": 2
    },
    {
      "type": "removed",
      "value": "brown",
      "count": 1
    },
    {
      "type": "added",
      "value": "red",
      "count": 1
    },
    {
      "type": "unchanged",
      "value": " fox",
      "count": 1
    }
  ],
  "hunks": [
    {
      "header": "@@ -1,1 +1,1 @@",
      "before_start": 1,
      "before_lines": 1,
      "after_start": 1,
      "after_lines": 1,
      "lines": [
        "-The quick brown fox",
        "\\ No newline at end of file",
        "+the quick red fox",
        "\\ No newline at end of file"
      ]
    }
  ],
  "unified": "--- before\n+++ after\n@@ -1,1 +1,1 @@\n-The quick brown fox\n\\ No newline at end of file\n+the quick red fox\n\\ No newline at end of file\n"
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "text_diff",
    "arguments": {
      "before": "The quick brown fox",
      "after": "the quick red fox",
      "mode": "words",
      "ignore_case": true
    }
  }
}