> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getversive.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Update randomizer

> Replace a randomizer's name, arms, weights, and targets

Replaces the randomizer's complete arm configuration. Pass every arm that should survive: an existing arm is matched by `branch_id`, an arm without one is added, and any existing arm you leave out is removed **together with its content**. A kept arm sent without a target is emptied the same way, so pass its current `question_id` or `question_group_id` back to keep what it shows. To take content out of a randomizer without deleting it, use [Remove randomizer](/api-reference/randomizers/remove-randomizer) with `mode: "ungroup"` instead.

<ParamField path="id" type="string" required>The randomizer ID.</ParamField>
<ParamField body="study_id" type="string" required>The study ID.</ParamField>
<ParamField body="name" type="string" required>The randomizer name (send the current name to keep it).</ParamField>

<ParamField body="arms" type="array" required>
  2 to 12 arms, the full final set. Each arm: optional `branch_id` (existing arm to keep; the arm's `id` from [List randomizers](/api-reference/randomizers/list-randomizers) is accepted in its place), `label`, `weight_basis_points` (all arms total exactly 10000), and one of `question_ids`, `question_id` (a single question, the shape [List randomizers](/api-reference/randomizers/list-randomizers) returns), or `question_group_id`, or none of them for an empty arm.
</ParamField>

<ParamField body="display_order" type="integer">New position in the parent. Omit to keep the current position.</ParamField>

### Response

The updated randomizer, same shape as [List randomizers](/api-reference/randomizers/list-randomizers).

<RequestExample>
  ```bash cURL theme={null}
  curl -X PUT https://api.getversive.com/api/v1/randomizers/5f1c2d3e-0000-4000-8000-000000000001 \
    -H "Authorization: Bearer $VERSIVE_API_KEY" \
    -H "Content-Type: application/json" \
    -d '{
      "study_id": "9b2f7c1e-4a4b-4f6e-9a1d-1c2d3e4f5a6b",
      "name": "Concept test",
      "arms": [
        { "branch_id": "7a0b1c2d-0000-4000-8000-000000000001", "label": "Concept A", "weight_basis_points": 7000, "question_ids": ["c1d2e3f4-0000-4000-8000-000000000001"] },
        { "branch_id": "7a0b1c2d-0000-4000-8000-000000000002", "label": "Concept B", "weight_basis_points": 3000, "question_group_id": "d4e5f6a7-0000-4000-8000-000000000002" }
      ]
    }'
  ```
</RequestExample>