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

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. Unrequested keys are omitted, not returned as null. id always comes back. Pass all for every requestable field. An unknown name is a 400. See Sparse fields.

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

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 — see the notes above.
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",
  "created_by_id": "16c61a3a-512a-48ac-b0be-b6b46fe6f430",
  "external_id": null,
  "external_source": null,
  "id": "b7e42a19-3c5d-4f80-9a26-8d1c0f4e7b53",
  "target_date": "2026-01-20",
  "title": "Example title"
}