> ## Documentation Index
> Fetch the complete documentation index at: https://algolia.com/llms.txt
> Use this file to discover all available pages before exploring further.

# A/B testing API version 3

> Differences between A/B testing APIs v2 and v3.

## Changes compared to the A/B testing API version 2

* **Time series endpoint**

  Analyze how your chosen metrics evolve over time while the test runs.

  New in v3: `GET /3/abtests/{id}/timeseries` with date range and metric selection.

* **Create A/B test**

  Choose which metrics the experiment should measure, and add statistical controls for evaluation.

  * v2: create a test by naming it, defining its variants, and setting an end date.
  * v3: in addition, you explicitly select the metrics to analyze (for example, conversion rate) and can configure statistical options such as minimum detectable effect (MDE), and multiple-testing correction.

* **Estimation endpoint**

  Estimate required sample sizes and duration to detect your target effect.

  * v2: basic estimator.
  * v3: uses your selected metrics and desired effect size/MDE for more tailored estimates.

* **Listing and retrieval**

  Same operations with more flexible sorting/filtering and responses that include your selected metrics and evaluation settings.

  * **Multi-variant testing**
    * v2: mixed setups such as A/A/B are rejected. You must either use the same index for all variants (for example, A/A/A) or use distinct indices for all variants (for example, A/B/C). Mixed shapes fail with an invalid configuration error.
    * v3: supports mixed shapes (for example, A/A/B).

**For details, see the API references:**

* [A/B testing API v2](/doc/rest-api/abtesting)
* [A/B testing API v3](/doc/rest-api/abtesting-v3)

## When to migrate

Migrate if you need any of the following:

* **Time series analysis** of test metrics.
* **Explicit metric selection** per test.
* **Minimum detectable effect (MDE)**, population filters, or multiple-testing correction.

If your v2 usage is stable and you don't need these new features, you can keep using v2.

## How to migrate

* **Do this in all cases:**

  * When creating a test, include the metrics to measure and any optional evaluation settings.
  * For planning, use the estimator with your desired effect size (MDE).
  * Use the time series endpoint if you need trends over time.

* **If you call the REST API directly:**

  Change base paths from `/2/abtests` to `/3/abtests` and adapt payloads.

* **If you use an API client:**

  * You need to use the latest major version of Algolia's [API clients](/doc/libraries/sdk/install).
  * If you're using an older version, you need to upgrade first.
  * The A/B testing API version 2 is available in all [supported versions](/doc/libraries/sdk/versions).