---
title: "Start a form A/B setup"
method: POST
path: "/form-ab-setups/{abSetupID}/start"
tags: ["Form A/B Setups"]
---

# Start a form A/B setup

`POST /form-ab-setups/{abSetupID}/start`

## Request

- Base URL: `https://api.omnisend.com/api`
- URL: `https://api.omnisend.com/api/form-ab-setups/{abSetupID}/start`
- Auth: one of:
  - OAuth 2
    - Client credentials
    - Token URL: `https://app.omnisend.com/oauth2/token` scopes: `forms.write`
  - API key in header `Authorization`

Start a form A/B test by ID. Launches the A/B setup so its variants begin serving to visitors according to
their weights, moving the setup to enabled status.
Starting a form A/B setup that has already been started returns a conflict.

An optional auto-close policy can be supplied in the request body. `endsAt` closes the test at a fixed
instant and must be in the future. `stopOnSignificance` closes the test as soon as one variant is a
statistically significant winner; on its own it is subject to a seven-day minimum runtime. Supply at least
one of the two, or omit `autoClose` entirely for a test that never closes automatically. The policy cannot
be changed after the test has started.

**Scopes:**
`forms.write`

**Rate Limiting:**
This endpoint is rate limited to 400 requests per minute.

## Path parameters

- `abSetupID` string, required

## Headers

- `Omnisend-Version` string, required

## Request body

- StartAbSetupRequest: Request to start a form A/B setup.
  - `autoClose` AbSetupAutoClose: Auto-close policy for a form A/B setup.
    - `endsAt` string: Instant at which the test closes automatically. Must be in the future when the test is started.
    - `stopOnSignificance` boolean: Close the test as soon as one variant is a statistically significant winner.

## Response `204`

Form A/B test started

## Other responses

- `400`: Request contains invalid or missing fields
- `401`: Authentication is missing or invalid
- `403`: Insufficient permissions for this operation
- `404`: Form A/B setup not found
- `409`: Form A/B setup is already started or cannot be started
- `410`: API version has been retired
- `429`: Rate limit exceeded
- `500`: Unexpected error occurred

---

[API](https://skmtc.dev/omnisend/apis/forms-api.md) - [All operations](https://skmtc.dev/omnisend/apis/forms-api/llms.txt) - [OpenAPI document](https://skmtc.dev/omnisend/apis/forms-api/revisions/9b53556b2e97?raw)