Create a milestone

POST/api/v2/workspaces/{slug}/projects/{project_id}/milestones/

Milestones mark dated checkpoints in a project. Create a milestone.

Path parameters

slug:requiredstring

The workspace slug. It appears in your Plane URLs. In https://app.plane.so/my-team/projects/, the slug is my-team.

project_id:requiredstring

The project the resource belongs to. Accepts the project UUID or its bare identifier, for example ENG.

Body parameters

title:requiredstring

The milestone's title.

Maximum 255 characters.

external_id:optionalstring

Your system's identifier for this record, for sync and import correlation.

Maximum 255 characters. Nullable.

external_source:optionalstring

The system external_id came from, for example github or jira.

Maximum 255 characters. Nullable.

target_date:optionalstring (date)

Planned due date, as YYYY-MM-DD.

Nullable.

Response shaping

fields:optionalstring

Comma-separated list of fields to return. Fields you don't request are left out of the response instead of coming back as null. id is always included. Pass all to get every requestable field. An unknown field name returns 400. See Sparse fields.

Requestable here: archived_at, created_at, created_by_id, external_id, external_source, id, target_date, title, updated_at, updated_by_id.

Scopes

projects.milestones:write

Errors

Status	Code	Cause
400	invalid_request	The request body or a query parameter failed validation.
401	unauthorized	Missing or invalid credentials.
402	payment_required	The feature this endpoint belongs to isn't enabled on your plan or is switched off.
403	forbidden	Your role or token scope doesn't allow this.
404	not_found	No such resource, or it's outside your tenant.
406	not_acceptable	The Accept header asks for a representation the API can't produce.
409	conflict	A business rule blocks the write.
413	payload_too_large	The request body is over the size limit.
415	unsupported_media_type	The Content-Type isn't one this endpoint accepts.
429	rate_limited	Throttled. Honor the Retry-After header before retrying.

Create a milestone

curl -X POST \
  "https://api.plane.so/api/v2/workspaces/my-team/projects/4af68566-94a4-4eb3-94aa-50dc9427067b/milestones/" \
  -H "X-Api-Key: $PLANE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "title": "Example title",
  "external_id": null,
  "external_source": null,
  "target_date": "2026-01-20"
}'

import requests

response = requests.post(
    "https://api.plane.so/api/v2/workspaces/my-team/projects/4af68566-94a4-4eb3-94aa-50dc9427067b/milestones/",
    headers={"X-Api-Key": "your-api-key"},
    json={
        "title": "Example title",
        "external_id": None,
        "external_source": None,
        "target_date": "2026-01-20"
    },
)
print(response.json())

const response = await fetch(
  "https://api.plane.so/api/v2/workspaces/my-team/projects/4af68566-94a4-4eb3-94aa-50dc9427067b/milestones/",
  {
    method: "POST",
    headers: {
      "X-Api-Key": "your-api-key",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      title: "Example title",
      external_id: null,
      external_source: null,
      target_date: "2026-01-20",
    }),
  },
);
const data = await response.json();

Response201

{
  "archived_at": null,
  "created_at": "2026-01-14T09:22:41.478363Z",
  "updated_at": "2026-01-14T09:22:41.478363Z",
  "created_by_id": "16c61a3a-512a-48ac-b0be-b6b46fe6f430",
  "updated_by_id": null,
  "external_id": null,
  "external_source": null,
  "id": "b7e42a19-3c5d-4f80-9a26-8d1c0f4e7b53",
  "target_date": "2026-01-20",
  "title": "Example title"
}