JSON Patch Examples

Real-world JSON Patch scenarios. Load any example into the tool, then generate the patch, apply it to the source, or verify it round-trips.

Add a field to a JSON object

The add operation inserts a value where none existed - the parent path must exist, the final key must not.

Add a New Field

Objects

Creating a property that did not exist with one add operation.

Source JSON

{
  "name": "John",
  "age": 25
}

Target JSON

{
  "name": "John",
  "age": 25,
  "email": "john@example.com"
}

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Learn more: The add operation

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Rename, move and copy values

Renaming a key is a move: relocate the value and the old key disappears. Copy duplicates a value without touching the source.

Rename a Key

Objects

The move operation removes a value from one path and adds it at another as a single operation.

Source JSON

{
  "username": "jdoe",
  "active": true
}

Target JSON

{
  "handle": "jdoe",
  "active": true
}

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Learn more: The move operation

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Duplicate a Value

Objects

The copy operation clones a value to a second location.

Source JSON

{
  "billing": {
    "address": {
      "city": "NYC",
      "zip": "10001"
    }
  }
}

Target JSON

{
  "billing": {
    "address": {
      "city": "NYC",
      "zip": "10001"
    }
  },
  "shipping": {
    "address": {
      "city": "NYC",
      "zip": "10001"
    }
  }
}

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Learn more: The copy operation

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Update values in a JSON object

The everyday case: change fields in place with replace, and add the ones that are missing.

User Profile Update

Common

Updating user information with new email and preferences.

Source JSON

{
  "id": 123,
  "name": "John Doe",
  "email": "john@example.com",
  "age": 25,
  "preferences": {
    "theme": "light",
    "notifications": true
  }
}

Target JSON

{
  "id": 123,
  "name": "John Smith",
  "email": "john.smith@example.com",
  "age": 26,
  "preferences": {
    "theme": "dark",
    "notifications": true,
    "language": "en"
  }
}

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Learn more: The replace operation

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Shopping Cart Operations

E-commerce

Adding items and applying discounts to a shopping cart.

Source JSON

{
  "items": [
    {
      "id": "item1",
      "name": "Laptop",
      "price": 999
    },
    {
      "id": "item2",
      "name": "Mouse",
      "price": 25
    }
  ],
  "total": 1024,
  "discount": 0
}

Target JSON

{
  "items": [
    {
      "id": "item1",
      "name": "Laptop",
      "price": 999
    },
    {
      "id": "item2",
      "name": "Mouse",
      "price": 25
    },
    {
      "id": "item3",
      "name": "Keyboard",
      "price": 75
    }
  ],
  "total": 1099,
  "discount": 10
}

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Learn more: The add operation

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Configuration Management

DevOps

Updating application configuration for production deployment.

Source JSON

{
  "database": {
    "host": "localhost",
    "port": 5432,
    "ssl": false
  },
  "cache": {
    "enabled": true,
    "ttl": 3600
  },
  "features": [
    "auth",
    "logging"
  ]
}

Target JSON

{
  "database": {
    "host": "prod-db.company.com",
    "port": 5432,
    "ssl": true,
    "pool_size": 20
  },
  "cache": {
    "enabled": true,
    "ttl": 7200
  },
  "features": [
    "auth",
    "logging",
    "analytics"
  ]
}

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Learn more: The add operation

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JSON Patch array operations

Arrays are where most patches go wrong: indexes shift as you edit, and the /- path appends without knowing the length.

Append to an Array

Arrays

Adding an item to the end of an array with the /- path.

Source JSON

{
  "tags": [
    "a",
    "b"
  ]
}

Target JSON

{
  "tags": [
    "a",
    "b",
    "c"
  ]
}

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Learn more: JSON Patch and arrays

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Remove an Array Element

Arrays

Deleting by index - later elements shift one position left.

Source JSON

{
  "queue": [
    "first",
    "second",
    "third"
  ]
}

Target JSON

{
  "queue": [
    "first",
    "third"
  ]
}

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Learn more: JSON Patch and arrays

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Update nested JSON properties

Deep values are patched with the full JSON Pointer path - one operation per value, no need to resend whole objects.

Update a Nested Property

Nested

Changing one deep value with the full JSON Pointer path.

Source JSON

{
  "user": {
    "name": "Ana",
    "address": {
      "city": "NYC",
      "zip": "10001"
    }
  }
}

Target JSON

{
  "user": {
    "name": "Ana",
    "address": {
      "city": "Boston",
      "zip": "10001"
    }
  }
}

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Learn more: JSON Patch and nested objects

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Escape special characters in JSON Pointer paths

Keys that contain / or ~ still work: RFC 6901 escapes them as ~1 and ~0.

Escaped JSON Pointer

Pointer

Patching a key that literally contains a slash - /a~1b.

Source JSON

{
  "a/b": {
    "timeout": 30
  }
}

Target JSON

{
  "a/b": {
    "timeout": 60
  }
}

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Learn more: JSON Pointer escaping

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Test a value before changing it

The test operation adds a precondition: if the value does not match, evaluation stops at that operation.

Test Before You Write

Safety

Stopping evaluation when the document is not in the expected state.

Source JSON

{
  "version": 1,
  "status": "draft"
}

Target JSON

{
  "version": 2,
  "status": "published"
}

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Learn more: The test operation

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Guarded Config Rollout

DevOps

Flip a production flag only if it is still off - test first, then change.

Source JSON

{
  "database": {
    "ssl": false,
    "pool_size": 10
  }
}

Target JSON

{
  "database": {
    "ssl": true,
    "pool_size": 20
  }
}

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Learn more: The test operation

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Using JSON Patch in Your Code

Get started with JSON Patch in JavaScript or Python in just a few lines.

JavaScript

Python

import { compare, applyPatch } from 'fast-json-patch'; // ESM
// Generate patch
const patch = compare(oldObj, newObj);
// Apply patch
const result = applyPatch(oldObj, patch).newDocument;

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JSON Patch Generator

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JSON Diff

Compare two JSON files online

Documentation

Complete RFC 6902 guide

Add Operation

Add values using JSON Patch

Remove Operation

Remove values using JSON Patch

Replace Operation

Replace values using JSON Patch