Fetch a single Holdout

1 min

GET

https://api.optimizely.com/flags/v1//projects/{project_id}/holdouts/{holdout_id}

Retrieves detailed information about a specific holdout by its unique ID within a project.

What you'll get:

Complete holdout configuration including traffic allocation, status, and settings
Associated experiment rules and their current states
Audience conditions and targeting criteria (if configured)
Metric tracking configuration and current values
Lifecycle timestamps (created, updated, started, ended)
RESTful links for related operations (update, delete, archive, etc.)

Holdout States:

Draft: Holdout is configured but not yet active
Running: Currently excluding traffic from experiments
Concluded: Finished collecting data, results available for analysis

Use Cases:

View complete holdout configuration before making changes
Monitor current status and performance metrics
Access experiment rules affected by this holdout
Retrieve data for analysis and reporting
Verify permissions for management operations via included links

This operation corresponds to the url or fetch_holdout_url property found in holdout list responses.

project_idintegerThe project identifier

holdout_idintegerThe holdout identifier

acceptstringGenerated from available response content types

200Successfully retrieved the holdout with all its configuration details. Response includes: <ul> <li>Core properties: ID, key, name, description, status, traffic allocation</li> <li>Lifecycle data: Created/updated timestamps, start/end times (if applicable)</li> <li>Configuration: Environment, audience conditions, metrics setup</li> <li>Experiment rules: Associated experiments and their allocation settings</li> <li>Management links: URLs for update, archive, delete operations (if authorized)</li> <li>System metadata: URN, project association, archive status</li> </ul> Link availability depends on user permissions: <ul> <li>Missing <code>update_url</code>: Cannot modify this holdout</li> <li>Missing <code>delete_url</code>: Cannot permanently delete</li> <li>Missing <code>archive_url</code>/<code>unarchive_url</code>: Cannot change archive status</li> </ul> Status-specific data: <ul> <li>Draft holdouts: Full configuration, no timing data</li> <li>Running holdouts: Includes <code>start_time</code>, active experiment rules</li> <li>Concluded holdouts: Includes both <code>start_time</code> and <code>end_time</code></li> </ul>

400Bad Request - Invalid request parameters or malformed holdout ID. Common causes: <ul> <li>Invalid <code>holdout_id</code> format (must be a positive integer)</li> <li>Invalid <code>project_id</code> format (must be a positive integer)</li> <li>Malformed request structure or unsupported query parameters</li> </ul>

401Invalid credentials

403Do not have permission to perform the operation

404Not Found - The specified holdout does not exist or you don't have access to it. Possible reasons: <ul> <li>Holdout ID does not exist in the specified project</li> <li>Project ID does not exist or you don't have access to it</li> <li>Holdout was permanently deleted</li> <li>Insufficient permissions to view this holdout</li> </ul>

curl --request GET \
     --url https://api.optimizely.com/flags/v1//projects/{project_id}/holdouts/{holdout_id} \
     --header 'accept: application/json'