Start Experiment

Enterprise

This endpoint is part of Countly Enterprise. To get access, contact sales or compare versions. Existing customers can reach the support portal with questions.

Endpoint

/i/ab-testing/start-experiment

Overview

Start an experiment and transition it from draft to running status. Creates cohorts for variant-goal tracking.

Authentication

Pass api_key or auth_token as a query parameter, or send countly-token as a header. See Authentication.

Permissions

• Update (ab_testing feature)

Request Parameters

Parameter	Type	Required	Description
api_key	String	Yes (or use auth_token)	API key for authentication
auth_token	String	Yes (or use api_key)	Auth token for authentication
app_id	String	Yes	Application identifier
experiment_id	String	Yes	Experiment ObjectId to start

Examples

Example 1: Start an Experiment

Request:

curl "https://your-server.com/i/ab-testing/start-experiment" \
  -d "api_key=YOUR_API_KEY" \
  -d "app_id=YOUR_APP_ID" \
  -d "experiment_id=5f9c8a3b4d1e2a001f3b4567"

Response

Success Response

{
  "result": "Success"
}

Response Fields

Field	Type	Description
result	String	Result message

Error Responses

• HTTP 500 - Experiment does not exist:

{
  "result": "The experiment does not exist."
}

• HTTP 400 - Already running:

{
  "result": "The experiment is already running."
}

• HTTP 400 - Already completed:

{
  "result": "The experiment is already complete."
}

• HTTP 500 - Failed to start:

{
  "result": "The experiment could not be started."
}

Behavior

• Creates cohorts for each variant-goal combination.
• Sets status to running and stores started_at timestamp.

Related Endpoints

• Stop Experiment
• Reset Experiment
• Remove Experiment

Implementation details

Database Collections

Collection	Used for	Data touched by this endpoint
countly_out.ab_testing_experiments{appId}	Primary:	Updates experiment status and start time.
countly.cohorts	Related:	Creates tracking cohorts for each variant-goal combination.