How to complete the challenge `PATCH /todos/id (200) merge-patch`

By Alan RichardsonUpdated 2026-07-30

Use PATCH with Content-Type: application/merge-patch+json when you want to send a JSON Merge Patch document.

The merge-patch may look similar to the application/json patch. But the main difference is the standard handling. Any API can use whatever conventions it wants to handle an application/json patch. The API Challenges app ignores your request if you try to set a mandatory field to null. But in a merge-patch+json standard, a null is a delete and you can't delete a mandatory field so you would see an error. Feel free to experiment with this after you complete the challenge.

PATCH /todos/id (200) merge-patch

Issue a PATCH request to update an existing todo using JSON Merge Patch.

Use PATCH /todos/{id} where {id} is an existing todo id.
Add Content-Type: application/merge-patch+json for the JSON Merge Patch standard.
Send a JSON object containing the fields to add, replace, or remove.
The response should be 200.
Fields that are not in the merge patch document should keep their existing values.
You can learn more about PATCH in the HTTP verbs tutorial.

Basic Instructions

Issue a PATCH request to:
- https://apichallenges.com/todos/{{firstTodoId}}
The request should have an X-CHALLENGER header so the challenge is tracked.
The request body can be a JSON Merge Patch object:

{
  "description": "patched with merge patch"
}

Try it now

If you don't know what todos are available then you can check by GET /todos. See the solution.

GET /todos to see what todos are available now

If you have already deleted all todos, create one using POST /todos. See the solution.

POST /todos to create a todo item for this challenge

PATCH /todos/{id} with JSON Merge Patch to update a todo

Example Request

> PATCH /todos/3 HTTP/1.1
> Host: apichallenges.com
> User-Agent: rest-client
> X-CHALLENGER: x-challenger-guid
> Content-Type: application/merge-patch+json
> Accept: application/json
>
> {"description":"patched with merge patch"}

Example Response

< HTTP/1.1 200 OK
< Content-Type: application/json
< Accept-Patch: application/json, application/merge-patch+json, application/json-patch+json
< X-Challenger: x-challenger-guid

Returned body:

{
  "id": 3,
  "title": "existing title",
  "doneStatus": false,
  "description": "patched with merge patch"
}

Experiment with this endpoint

How to complete the challenge PATCH /todos/id (200) merge-patch