Tools to A/B test LLMs: ABTO, OpenRouter, LiteLLM and Langfuse compared
Comparing LLMs can mean switching models easily, scoring answers, or measuring how real users respond. Each tool below is built around a different one of these.
| Tool | Built around | Pick it when |
|---|---|---|
| ABTO | Compare real outcomes from your users for each model | You want to know how switching models changes revenue and sign-ups |
| OpenRouterFull comparison | Call models from many companies through one API | You want to call and pay for models from many companies in one place |
| LiteLLMFull comparison | Call many model APIs in one format | You want to run the call path yourself and manage keys and budgets in detail |
| LangfuseFull comparison | Tracing, prompt management and evaluation for LLM calls | You want to record calls and evaluate answer quality during development |
Descriptions of other tools are based on each company's public documentation as of October 2026. Features and pricing can change, so check their documentation for the latest details.
Other comparisons
- OpenRouter vs ABTO: what is the difference?
- LiteLLM vs ABTO: what is the difference?
- Langfuse vs ABTO: what is the difference?