---
title: Start experiment
description: Start an experiment.
breadcrumbs: Documentation > API > Start experiment
---

> For the complete documentation index, see [llms.txt](https://dnd37xeb23o8n.cloudfront.net/stefon.simmons/docs-astro-web-10435/llms.txt).

# Start experiment

{% callout %}
This product or feature is not supported for the following sites: app.ddog-gov.com, us2.ddog-gov.com
{% /callout %}

## v2 (latest)

| Datadog site      | API endpoint                                                                |
| ----------------- | --------------------------------------------------------------------------- |
| 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 |
| app.datadoghq.eu  | POST https://api.datadoghq.eu/api/v2/experiments/{experiment_id}/start      |
| 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 |
| uk1.datadoghq.com | POST https://api.uk1.datadoghq.com/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  |

### 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://dnd37xeb23o8n.cloudfront.net/stefon.simmons/docs-astro-web-10435/fr/api/latest/scopes.md#experiments) to access this endpoint.

### Arguments

#### Path Parameters

| Field                      | Type   | Description                 |
| -------------------------- | ------ | --------------------------- |
| experiment_id [*required*] | string | The UUID of the experiment. |

### Request

#### Body Data

{% tabs %}
{% tab label="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`. Default: `start-experiment-request`. |
{% /tab %}

{% tab label="Example" %}
```json
{
  "data": {
    "id": "string",
    "type": "start-experiment-request"
  }
}
```
{% /tab %}
{% /tabs %}

### Response

{% tabs %}
{% tab label="204" %}
The experiment was started.
{% /tab %}

{% tab label="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.

{% tabs %}
{% tab label="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 label="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 %}
{% /tabs %}
{% /tab %}

{% tab label="401" %}
Missing or invalid authentication (dd-api-key + dd-application-key headers, or a valid user session).

{% tabs %}
{% tab label="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 label="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 %}
{% /tabs %}
{% /tab %}

{% tab label="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.

{% tabs %}
{% tab label="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 label="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 %}
{% /tabs %}
{% /tab %}

{% tab label="404" %}
No experiment with this ID exists for the organization.

{% tabs %}
{% tab label="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 label="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 %}
{% /tabs %}
{% /tab %}

{% tab label="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).

{% tabs %}
{% tab label="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 label="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 %}
{% /tabs %}
{% /tab %}

{% tab label="429" %}
Too many requests

{% tabs %}
{% tab label="Model" %}
API error response.

| Field               | Type     | Description       |
| ------------------- | -------- | ----------------- |
| errors [*required*] | [string] | A list of errors. |
{% /tab %}

{% tab label="Example" %}
```json
{
  "errors": [
    "Bad Request"
  ]
}
```
{% /tab %}
{% /tabs %}
{% /tab %}
{% /tabs %}

### Code Example

{% tabs %}
{% tab label="Curl" %}
```bash
# Path parameters
export experiment_id="550e8400-e29b-41d4-a716-446655440000"

# Set your Datadog site and credentials
export DD_SITE="datadoghq.com" # Or us3.datadoghq.com, us5.datadoghq.com, datadoghq.eu, ap1.datadoghq.com, ap2.datadoghq.com, uk1.datadoghq.com, ddog-gov.com, us2.ddog-gov.com
# Use a Personal Access Token or Service Access Token
export DD_BEARER_TOKEN="<PERSONAL_ACCESS_TOKEN OR SERVICE_ACCESS_TOKEN>"

curl -X POST "https://api.${DD_SITE}/api/v2/experiments/${experiment_id}/start" \
-H "Content-Type: application/json" \
-H "Authorization: Bearer ${DD_BEARER_TOKEN}" \
-d @- << EOF
{
  "data": {
    "type": "start-experiment-request"
  }
}
EOF
```
{% /tab %}

{% tab label="Go" %}
```go
// Start experiment returns "The experiment was started." response

package main

import (
	"context"
	"fmt"
	"os"

	"github.com/DataDog/datadog-api-client-go/v2/api/datadog"
	"github.com/DataDog/datadog-api-client-go/v2/api/datadogV2"
	"github.com/google/uuid"
)

func main() {
	// there is a valid "configured_experiment" in the system
	ConfiguredExperimentDataID := uuid.MustParse(os.Getenv("CONFIGURED_EXPERIMENT_DATA_ID"))

	ctx := datadog.NewDefaultContext(context.Background())
	ctx = context.WithValue(ctx, datadog.ContextAccessToken, os.Getenv("DD_BEARER_TOKEN"))
	configuration := datadog.NewConfiguration()
	apiClient := datadog.NewAPIClient(configuration)
	api := datadogV2.NewExperimentsApi(apiClient)
	r, err := api.StartExperiment(ctx, ConfiguredExperimentDataID, *datadogV2.NewStartExperimentOptionalParameters())

	if err != nil {
		fmt.Fprintf(os.Stderr, "Error when calling `ExperimentsApi.StartExperiment`: %v\n", err)
		fmt.Fprintf(os.Stderr, "Full HTTP response: %v\n", r)
	}
}
```

#### Instructions

First [install the library and its dependencies](https://dnd37xeb23o8n.cloudfront.net/api/latest.md?code-lang=go) and then save the example to `main.go` and run following commands:

```bash
DD_SITE="datadoghq.com" DD_BEARER_TOKEN="<PERSONAL_ACCESS_TOKEN OR SERVICE_ACCESS_TOKEN>" go run "main.go"
```
{% /tab %}

{% tab label="Java" %}
```java
// Start experiment returns "The experiment was started." response

import com.datadog.api.client.ApiClient;
import com.datadog.api.client.ApiException;
import com.datadog.api.client.v2.api.ExperimentsApi;
import java.util.UUID;

public class Example {
  public static void main(String[] args) {
    ApiClient defaultClient = ApiClient.getDefaultApiClient();
    defaultClient.setAccessToken(System.getenv("DD_BEARER_TOKEN"));
    ExperimentsApi apiInstance = new ExperimentsApi(defaultClient);

    // there is a valid "configured_experiment" in the system
    UUID CONFIGURED_EXPERIMENT_DATA_ID = null;
    try {
      CONFIGURED_EXPERIMENT_DATA_ID =
          UUID.fromString(System.getenv("CONFIGURED_EXPERIMENT_DATA_ID"));
    } catch (IllegalArgumentException e) {
      System.err.println("Error parsing UUID: " + e.getMessage());
    }

    try {
      apiInstance.startExperiment(CONFIGURED_EXPERIMENT_DATA_ID);
    } catch (ApiException e) {
      System.err.println("Exception when calling ExperimentsApi#startExperiment");
      System.err.println("Status code: " + e.getCode());
      System.err.println("Reason: " + e.getResponseBody());
      System.err.println("Response headers: " + e.getResponseHeaders());
      e.printStackTrace();
    }
  }
}
```

#### Instructions

First [install the library and its dependencies](https://dnd37xeb23o8n.cloudfront.net/api/latest.md?code-lang=java) and then save the example to `Example.java` and run following commands:

```bash
DD_SITE="datadoghq.com" DD_BEARER_TOKEN="<PERSONAL_ACCESS_TOKEN OR SERVICE_ACCESS_TOKEN>" java "Example.java"
```
{% /tab %}

{% tab label="Python" %}
```python
"""
Start experiment returns "The experiment was started." response
"""

from os import environ
from datadog_api_client import ApiClient, Configuration
from datadog_api_client.v2.api.experiments_api import ExperimentsApi

# there is a valid "configured_experiment" in the system
CONFIGURED_EXPERIMENT_DATA_ID = environ["CONFIGURED_EXPERIMENT_DATA_ID"]

configuration = Configuration()
configuration.access_token = environ["DD_BEARER_TOKEN"]
with ApiClient(configuration) as api_client:
    api_instance = ExperimentsApi(api_client)
    api_instance.start_experiment(
        experiment_id=CONFIGURED_EXPERIMENT_DATA_ID,
    )
```

#### Instructions

First [install the library and its dependencies](https://dnd37xeb23o8n.cloudfront.net/api/latest.md?code-lang=python) and then save the example to `example.py` and run following commands:

```bash
DD_SITE="datadoghq.com" DD_BEARER_TOKEN="<PERSONAL_ACCESS_TOKEN OR SERVICE_ACCESS_TOKEN>" python3 "example.py"
```
{% /tab %}

{% tab label="Ruby" %}
```ruby
# Start experiment returns "The experiment was started." response

require "datadog_api_client"
DatadogAPIClient.configure do |config|
  config.access_token = ENV["DD_BEARER_TOKEN"]
end
api_instance = DatadogAPIClient::V2::ExperimentsAPI.new

# there is a valid "configured_experiment" in the system
CONFIGURED_EXPERIMENT_DATA_ID = ENV["CONFIGURED_EXPERIMENT_DATA_ID"]
api_instance.start_experiment(CONFIGURED_EXPERIMENT_DATA_ID)
```

#### Instructions

First [install the library and its dependencies](https://dnd37xeb23o8n.cloudfront.net/api/latest.md?code-lang=ruby) and then save the example to `example.rb` and run following commands:

```bash
DD_SITE="datadoghq.com" DD_BEARER_TOKEN="<PERSONAL_ACCESS_TOKEN OR SERVICE_ACCESS_TOKEN>" rb "example.rb"
```
{% /tab %}

{% tab label="Rust" %}
```rust
// Start experiment returns "The experiment was started." response
use datadog_api_client::datadog;
use datadog_api_client::datadogV2::api_experiments::ExperimentsAPI;
use datadog_api_client::datadogV2::api_experiments::StartExperimentOptionalParams;

#[tokio::main]
async fn main() {
    // there is a valid "configured_experiment" in the system
    let configured_experiment_data_id =
        uuid::Uuid::parse_str(&std::env::var("CONFIGURED_EXPERIMENT_DATA_ID").unwrap())
            .expect("Invalid UUID");
    let configuration = datadog::Configuration::new();
    let api = ExperimentsAPI::with_config(configuration);
    let resp = api
        .start_experiment(
            configured_experiment_data_id.clone(),
            StartExperimentOptionalParams::default(),
        )
        .await;
    if let Ok(value) = resp {
        println!("{:#?}", value);
    } else {
        println!("{:#?}", resp.unwrap_err());
    }
}
```

#### Instructions

First [install the library and its dependencies](https://dnd37xeb23o8n.cloudfront.net/api/latest.md?code-lang=rust) and then save the example to `src/main.rs` and run following commands:

```bash
DD_SITE="datadoghq.com" DD_API_KEY="<DD_API_KEY>" DD_APP_KEY="<DD_APP_KEY>" cargo run
```
{% /tab %}
{% /tabs %}