Weights & Biases

✓ Editorially verified

The ML experiment tracker, now with LLM eval features.

Freemium· Free personal; team from $50/mo per seatEvaluationPlatform (any LLM)8.4 / 10

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Best for

Pick W&B when your team already uses it for traditional ML and you want to add LLM eval on the same platform.

Skip if

Skip it for greenfield LLM-only work — Braintrust or LangSmith are more focused.

Weights & Biases is the industry-standard ML experiment tracker — used by virtually every serious research team and most ML production teams. The W&B Weave product adds LLM-native eval and prompt management on top of the core experiment tracking, which makes W&B viable for teams that want one platform for traditional ML + LLM evaluation.

For organisations already on W&B for traditional ML, adding Weave for LLM evals is the path of least resistance. The mature, reliable platform handles team management, access control, and integrations with most ML frameworks better than any LLM-native alternative.

The trade-off is that Weave is newer than W&B's traditional-ML features. LLM-specific features are catching up to the Braintrust / LangSmith level but aren't quite there yet. For teams not already on W&B, the LLM-native competitors are usually a better starting point.

Editor's take

W&B is the established player adding LLM features to a traditional-ML moat. The right pick for teams already on the platform, less obvious for teams starting from scratch on LLM eval.

— The AI Tool Bible editorial team