Playgrounds in Braintrust facilitate A/B testing by enabling users to compare different prompt variants simultaneously, allowing for the evaluation of prompt improvements through real quality scores before deployment. This process is crucial when iterating on prompts to catch regressions, comparing performance across different models, or evaluating changes against test datasets. The unpredictable effects of prompt development are transformed into measurable comparisons through A/B testing, which is supported both natively in the web interface and via the SDK, catering to both product managers and engineers. Users can experiment visually with prompts, models, and scorers to observe how changes affect key metrics, or they can use code to integrate A/B testing into CI/CD pipelines. By running multiple variants in parallel, Braintrust provides immediate insights into quality scores, latency, token usage, and custom metrics, helping users catch regressions and identify improvements efficiently. The platform supports testing against real-world datasets to ensure representative inputs, and its native CI/CD integration helps prevent regressions from reaching production. Whether using the web UI or the SDK, users can systematically improve prompts and make informed decisions about model performance based on data rather than assumptions.