# JSON merge patch

`json-merge-patch` · version 1.0.0 · JSON & JSONL · free, no key needed

Apply an RFC 7396 JSON Merge Patch to a JSON value.

**Use when you need to: json merge patch · apply json merge patch · rfc 7396 merge patch.**

## Supported

- json merge patch
- apply json merge patch
- rfc 7396 merge patch

## Not supported

- json patch rfc 6902
- elementwise array merge
- json pointer set
- fuzzy merge
- read files
- fetch urls

## Behavior

- If patch is not a JSON object, including when it is an array or null, the result is the patch.
- If patch is an object and target is not a non-array object, merging starts from an empty object.
- A null patch value deletes that own key; deleting a missing key is a no-op.
- Nested objects are merged recursively in Object.keys order; arrays and other non-objects replace.
- Result objects are null-prototype copies. Inputs are not mutated.
- Prototype-like names are ordinary own keys.
- JSON numbers must be safe integers. Depth is at most 16 and at most 5000 own keys are visited per value.

## Input

- `target` (any, required)
- `patch` (any, required)

## Output

- `value` (any, required)

## Limits

- max depth: 16
- max own keys visited: 5000
- max output bytes: 1048576

## Example

Request input:

```json
{
  "target": {
    "title": "Goodbye!",
    "author": {
      "givenName": "John",
      "familyName": "Doe"
    },
    "tags": [
      "example",
      "sample"
    ],
    "content": "This will be unchanged"
  },
  "patch": {
    "title": "Hello!",
    "phoneNumber": "+01-123-456-7890",
    "author": {
      "familyName": null
    },
    "tags": [
      "example"
    ]
  }
}
```

Response:

```json
{
  "result": {
    "value": {
      "title": "Hello!",
      "author": {
        "givenName": "John"
      },
      "tags": [
        "example"
      ],
      "content": "This will be unchanged",
      "phoneNumber": "+01-123-456-7890"
    }
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "json-merge-patch",
  "version": "1.0.0",
  "input": {
    "target": {
      "title": "Goodbye!",
      "author": {
        "givenName": "John",
        "familyName": "Doe"
      },
      "tags": [
        "example",
        "sample"
      ],
      "content": "This will be unchanged"
    },
    "patch": {
      "title": "Hello!",
      "phoneNumber": "+01-123-456-7890",
      "author": {
        "familyName": null
      },
      "tags": [
        "example"
      ]
    }
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/json-merge-patch/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"target":{"title":"Goodbye!","author":{"givenName":"John","familyName":"Doe"},"tags":["example","sample"],"content":"This will be unchanged"},"patch":{"title":"Hello!","phoneNumber":"+01-123-456-7890","author":{"familyName":null},"tags":["example"]}}'
```

The machine-readable contract is at [/v1/tools/json-merge-patch/versions/1.0.0](/v1/tools/json-merge-patch/versions/1.0.0).

### CLI

```sh
node cli.mjs run json-merge-patch 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [Array to JSONL](/tools/array-to-jsonl): Serialize an array of JSON-safe values as JSON Lines text.
- [JSON array anti join](/tools/json-array-anti-join): Anti join two JSON arrays of objects on exact keys.
- [JSON array concat](/tools/json-array-concat): Concatenate multiple JSON arrays of objects into one.
- [JSON array count](/tools/json-array-count): Count structural occurrences in a JSON array in first-seen order.
- [JSON array distinct by](/tools/json-array-distinct-by): Deduplicate a JSON array of objects based on specific keys.
- [JSON array drop keys](/tools/json-array-drop-keys): Remove specific keys from each object in a JSON array.