Updated March 10, 2026
Opik by Comet is an open-source LLM evaluation and observability platform. It provides tracing, evaluation scoring, dataset management, and experiment tracking for LLM applications. Opik supports automated LLM-as-judge evaluations and integrates with popular frameworks like LangChain and LlamaIndex.
Weights & Biases (W&B) is the leading experiment tracking and ML operations platform, now extended to LLM applications. W&B Traces provides observability for LLM pipelines, while W&B Weave offers evaluation and production monitoring. The platform also supports model training tracking, hyperparameter sweeps, and artifact management, making it a comprehensive MLOps solution.
Core capabilities each platform advertises.
What each tool does well, and the limitations to keep in mind.
Pros
Cons
Pros
Cons
Choose Opik if you wantChoose if you want
Choose Weights & if you wantChoose if you want
Respan lets you trace LLM and agent calls across any model or framework, A/B test prompts on production traffic, and route requests across 500+ models through one gateway.