# A/B testing prompts

**Source:** https://promtable.com/glossary/ab-testing-prompts

> A/B testing prompts runs two prompt variants against the same input distribution and compares scored outputs, attributing quality differences to the prompt change.

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A/B testing prompts runs two prompt variants against the same input distribution and compares scored outputs, attributing quality differences to the prompt change.

Production A/B testing for prompts in 2026 either splits offline golden-set runs (cheap, fast feedback) or splits live production traffic (slower, real signal). Live splits need traceable version IDs in tracing data, automated rubric scoring on samples, and a stopping rule (Bayesian or frequentist) before promoting a variant. Tools: Braintrust, Vellum, Statsig + manual rubrics, internal A/B platforms. The discipline is the same as feature A/B but with rubric-based outcome metrics instead of click-through.

## When to use

- High-traffic production LLM features.
- Choosing between prompt families before commit.

## Common mistakes

- Splitting traffic without tracing the variant ID — can't attribute outcomes.
- Stopping the test too early — LLM outcome variance is high; need more samples than UI A/B.

## Related terms

- [evals](https://promtable.com/glossary/evals)
- [prompt-versioning](https://promtable.com/glossary/prompt-versioning)
- [llm-jury](https://promtable.com/glossary/llm-jury)

*Last updated: 2026-06-01*
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Original page: https://promtable.com/glossary/ab-testing-prompts
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