2024 Optimizely Feature Experimentation release notes

  • Updated
  • Optimizely Feature Experimentation

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Renamed the following Optimizely REST API endpoints to clarify they archive the entities instead of deleting them:

Feature Experimentation REST API enhancements

  • Added variations and metrics to the response for the List Rules endpoint – The /rules endpoint now returns high-level information on variations for flag rules and metrics for A/B tests and multi-armed bandits. For example,
            "name": "Repeat Buyers Test",
            // ...
            "variations": {
                "off": {
                    "key": "off",
                    "name": "Off",
                    "percentage_included": 3333,
                    "variation_id": 329457
                "repeat_buyers_1": {
                    "key": "repeat_buyers_1",
                    "name": "Repeat Buyers 1",
                    "percentage_included": 3333,
                    "variation_id": 373838
                "repeat_buyers_2": {
                    "key": "repeat_buyers_2",
                    "name": "Repeat Buyers 2",
                    "percentage_included": 3334,
                    "variation_id": 373839
            "metrics": [
                    "event_id": 27053200523,
                    "scope": "visitor",
                    "aggregator": "unique",
                    "winning_direction": "increasing",                 
    "display_title": "addToCart" }, { "scope": "visitor", "aggregator": "sum", "winning_direction": "increasing", "display_title": "Overall Revenue" } ]
  • Updated the API response for the List Reports endpoint – The revision field was previously documented in the API reference but not actually returned by the API. The API response was updated to return the revision field.
  • Updated documentation for layer_experiment_id – The following API endpoints return the layer_experiment_id field, but it was not consistently documented. Updated the Feature Experimentation API reference to ensure consistency with actual API behavior.


  • Released the ability to sign up for email notifications when Optimizely Experimentation detects a sample ratio mismatch in your running experiments. See Enable email notifications in Optimizely Experimentation.
  • Updated the /reports endpoint to return tokens for pagination of results as a stand-alone element (previously only included in URLs in response). This makes it easier to programmatically form URLs to request reports from other pages. 
    • Also updated the /reports endpoint to return valid endpoints for fetch_results_api_url and fetch_results_ui_url to fetch experiment results with subsequent API calls.
  • Released lifecycle management for flags and rules to open beta. This introduces new statutes and makes it easier to see the state of your experiments. See Manage flags and Manage rules.



Released the ability to link a hypothesis in Experiment Collaboration with an experiment in Optimizely Feature Experimentation.


Released the ability to use bucketing IDs to decouple user bucketing from user identification.  


  • Increased the allowlist total from 10 to 50 users.
  • Released the Scheduling API, which lets you list, create, update, and delete scheduled changes for your Feature Experimentation flags and rules.


Breaking change for SDKs

Released a major version update for the following SDKs. See the SDK's GitHub release notes for details, including breaking changes.

The release includes Advanced Audience Targeting, which was renamed to Real-Time Segments for Feature Experimentation in May 2024