--- title: Start experiment description: Datadog, the leading service for cloud-scale monitoring. breadcrumbs: Docs > API Reference > Experiments --- > For the complete documentation index, see [llms.txt](https://docs.datadoghq.com/llms.txt). {% callout %} # Important note for users on the following Datadog sites: app.ddog-gov.com, us2.ddog-gov.com {% alert level="danger" %} This product is not supported for your selected [Datadog site](https://docs.datadoghq.com/getting_started/site.md). ({% placeholder "user-datadog-site-name" /%}). {% /alert %} {% /callout %} # Start experiment{% #start-experiment %} {% tab title="v2" %} | Datadog site | API endpoint | | ----------------- | --------------------------------------------------------------------------- | | ap1.datadoghq.com | POST https://api.ap1.datadoghq.com/api/v2/experiments/{experiment_id}/start | | ap2.datadoghq.com | POST https://api.ap2.datadoghq.com/api/v2/experiments/{experiment_id}/start | | app.datadoghq.eu | POST https://api.datadoghq.eu/api/v2/experiments/{experiment_id}/start | | app.ddog-gov.com | POST https://api.ddog-gov.com/api/v2/experiments/{experiment_id}/start | | us2.ddog-gov.com | POST https://api.us2.ddog-gov.com/api/v2/experiments/{experiment_id}/start | | uk1.datadoghq.com | POST https://api.uk1.datadoghq.com/api/v2/experiments/{experiment_id}/start | | app.datadoghq.com | POST https://api.datadoghq.com/api/v2/experiments/{experiment_id}/start | | us3.datadoghq.com | POST https://api.us3.datadoghq.com/api/v2/experiments/{experiment_id}/start | | us5.datadoghq.com | POST https://api.us5.datadoghq.com/api/v2/experiments/{experiment_id}/start | ### Overview Start an experiment. The experiment is started exactly as it is configured; this endpoint accepts no attributes, and a request body carrying any is rejected rather than ignored. Set the run window, duration, or variants with PATCH /api/v2/experiments/{experiment_id} before starting. An unconfigured draft returns HTTP 409. Configure either warehouse_exposure_configuration or datadog_flag_configuration, plus the required experiment fields, before starting. Start validation errors can include meta.configuration_pointer to identify a field on the experiment to correct. For a flag-backed experiment this enables the linked feature flag's environment, clears any stored variant override on it, and starts the allocation's rollout. The request is idempotent: an experiment that is already running or ready for a decision still returns 204, so a retry after a timeout is safe. One exception: an experiment scheduled to start is accepted only when it is backed by your own feature flag; a Datadog-flag experiment in that state returns 409 because its stored state and flag allocation disagree. Cancel and conclude are not idempotent and return 409 when repeated. This endpoint requires the `product_analytics_experiments_write` permission. OAuth apps require the `product_analytics_experiments_write` authorization [scope](https://docs.datadoghq.com/api/latest/scopes.md#experiments) to access this endpoint. ### Arguments #### Path Parameters | Name | Type | Description | | ------------------------------- | ------ | --------------------------- | | experiment_id [*required*] | string | The UUID of the experiment. | ### Request #### Body Data {% tab title="Model" %} | Parent field | Field | Type | Description | | ------------ | ---------------------- | ------ | --------------------------------------------------------------------------------------- | | | data [*required*] | object | JSON:API resource containing the experiment identity. | | data | id | string | ID of the experiment. | | data | type [*required*] | enum | Start experiment request resource type. Allowed enum values: `start-experiment-request` | {% /tab %} {% tab title="Example" %} ```json { "data": { "id": "string", "type": "start-experiment-request" } } ``` {% /tab %} ### Response {% tab title="204" %} The experiment was started. {% /tab %} {% tab title="400" %} Malformed experiment ID, a request body carrying attributes this endpoint does not accept, or an experiment managed by a specialized workflow that cannot use this start endpoint. {% tab title="Model" %} API error response. | Parent field | Field | Type | Description | | ------------ | ------------------------ | -------- | ------------------------------------------------------------------------------- | | | errors [*required*] | [object] | A list of errors. | | errors | detail | string | A human-readable explanation specific to this occurrence of the error. | | errors | meta | object | Non-standard meta-information about the error | | errors | source | object | References to the source of the error. | | source | header | string | A string indicating the name of a single request header which caused the error. | | source | parameter | string | A string indicating which URI query parameter caused the error. | | source | pointer | string | A JSON pointer to the value in the request document that caused the error. | | errors | status | string | Status code of the response. | | errors | title | string | Short human-readable summary of the error. | {% /tab %} {% tab title="Example" %} ```json { "errors": [ { "detail": "Missing required attribute in body", "meta": {}, "source": { "header": "Authorization", "parameter": "limit", "pointer": "/data/attributes/title" }, "status": "400", "title": "Bad Request" } ] } ``` {% /tab %} {% /tab %} {% tab title="401" %} Missing or invalid authentication (dd-api-key + dd-application-key headers, or a valid user session). {% tab title="Model" %} API error response. | Parent field | Field | Type | Description | | ------------ | ------------------------ | -------- | ------------------------------------------------------------------------------- | | | errors [*required*] | [object] | A list of errors. | | errors | detail | string | A human-readable explanation specific to this occurrence of the error. | | errors | meta | object | Non-standard meta-information about the error | | errors | source | object | References to the source of the error. | | source | header | string | A string indicating the name of a single request header which caused the error. | | source | parameter | string | A string indicating which URI query parameter caused the error. | | source | pointer | string | A JSON pointer to the value in the request document that caused the error. | | errors | status | string | Status code of the response. | | errors | title | string | Short human-readable summary of the error. | {% /tab %} {% tab title="Example" %} ```json { "errors": [ { "detail": "Missing required attribute in body", "meta": {}, "source": { "header": "Authorization", "parameter": "limit", "pointer": "/data/attributes/title" }, "status": "400", "title": "Bad Request" } ] } ``` {% /tab %} {% /tab %} {% tab title="403" %} Authenticated caller lacks the product_analytics_experiments_write permission, lacks permission to edit this experiment, or lacks contribute permission on the feature flag owning its allocation. {% tab title="Model" %} API error response. | Parent field | Field | Type | Description | | ------------ | ------------------------ | -------- | ------------------------------------------------------------------------------- | | | errors [*required*] | [object] | A list of errors. | | errors | detail | string | A human-readable explanation specific to this occurrence of the error. | | errors | meta | object | Non-standard meta-information about the error | | errors | source | object | References to the source of the error. | | source | header | string | A string indicating the name of a single request header which caused the error. | | source | parameter | string | A string indicating which URI query parameter caused the error. | | source | pointer | string | A JSON pointer to the value in the request document that caused the error. | | errors | status | string | Status code of the response. | | errors | title | string | Short human-readable summary of the error. | {% /tab %} {% tab title="Example" %} ```json { "errors": [ { "detail": "Missing required attribute in body", "meta": {}, "source": { "header": "Authorization", "parameter": "limit", "pointer": "/data/attributes/title" }, "status": "400", "title": "Bad Request" } ] } ``` {% /tab %} {% /tab %} {% tab title="404" %} No experiment with this ID exists for the organization. {% tab title="Model" %} API error response. | Parent field | Field | Type | Description | | ------------ | ------------------------ | -------- | ------------------------------------------------------------------------------- | | | errors [*required*] | [object] | A list of errors. | | errors | detail | string | A human-readable explanation specific to this occurrence of the error. | | errors | meta | object | Non-standard meta-information about the error | | errors | source | object | References to the source of the error. | | source | header | string | A string indicating the name of a single request header which caused the error. | | source | parameter | string | A string indicating which URI query parameter caused the error. | | source | pointer | string | A JSON pointer to the value in the request document that caused the error. | | errors | status | string | Status code of the response. | | errors | title | string | Short human-readable summary of the error. | {% /tab %} {% tab title="Example" %} ```json { "errors": [ { "detail": "Missing required attribute in body", "meta": {}, "source": { "header": "Authorization", "parameter": "limit", "pointer": "/data/attributes/title" }, "status": "400", "title": "Bad Request" } ] } ``` {% /tab %} {% /tab %} {% tab title="409" %} The experiment cannot be started from its current state, its stored setup is incomplete (missing subject type, primary metric, variants, assignment source, or run window), its linked feature flag environment requires an approval, or that flag has a pending suggestion for a property this would change (environment status, override variant, rollout, or allocations). {% tab title="Model" %} API error response. | Parent field | Field | Type | Description | | ------------ | ------------------------ | -------- | ------------------------------------------------------------------------------- | | | errors [*required*] | [object] | A list of errors. | | errors | detail | string | A human-readable explanation specific to this occurrence of the error. | | errors | meta | object | Non-standard meta-information about the error | | errors | source | object | References to the source of the error. | | source | header | string | A string indicating the name of a single request header which caused the error. | | source | parameter | string | A string indicating which URI query parameter caused the error. | | source | pointer | string | A JSON pointer to the value in the request document that caused the error. | | errors | status | string | Status code of the response. | | errors | title | string | Short human-readable summary of the error. | {% /tab %} {% tab title="Example" %} ```json { "errors": [ { "detail": "Missing required attribute in body", "meta": {}, "source": { "header": "Authorization", "parameter": "limit", "pointer": "/data/attributes/title" }, "status": "400", "title": "Bad Request" } ] } ``` {% /tab %} {% /tab %} {% tab title="429" %} Too many requests {% tab title="Model" %} API error response. | Field | Type | Description | | ------------------------ | -------- | ----------------- | | errors [*required*] | [string] | A list of errors. | {% /tab %} {% tab title="Example" %} ```json { "errors": [ "Bad Request" ] } ``` {% /tab %} {% /tab %} ### Code Example ##### \## default # \# Path parameters export experiment_id="550e8400-e29b-41d4-a716-446655440000" \# Use a Personal Access Token or Service Access Token export DD_BEARER_TOKEN="" \# Curl command curl -X POST "https://api.datadoghq.com/api/v2/experiments/${experiment_id}/start" \ -H "Content-Type: application/json" \ -H "Authorization: Bearer ${DD_BEARER_TOKEN}" \ -d @- << EOF { "data": { "type": "start-experiment-request" } } EOF {% /tab %}