Weights & Biases
FreeExperiment tracking and LLMOps
FreeFree tier
Inputs: code
About Weights & Biases
Weights & Biases (W&B) provides an end-to-end AI developer platform for experiment tracking, model management, and LLMOps. Its Weave offering delivers observability and continuous improvement for production agents, with end-to-end tracing, built-in safety and quality guardrails, a flexible evaluation framework, and a playground for testing prompts and models. The platform supports the full ML lifecycle from training and fine-tuning to deployment and monitoring, and offers both cloud-hosted and self-hosted options with a free tier for personal projects.
Key Features
Experiment tracking and model versioning with W&B Artifacts
Weave observability for production agents (traces, sessions, turns, steps, tools, sub-agents)
Built-in safety and quality guardrails (toxicity, bias, PII, hallucination, coherence, fluency, context relevance)
Flexible evaluation framework with score comparisons and regressions detection
Playground for exploring LLMs, custom models, and prompt techniques using production traces
Leaderboards to aggregate evaluations and share best-performing models across teams
Production monitoring with alerts via Slack and webhook automations
Autonomous improvement loops via MCP server and W&B skills for coding agents like Claude Code
Collaborative dashboards and reports (W&B Reports and Tables)
CI/CD automations, team-based access controls, and service accounts (Pro and Enterprise)
Pros & Cons
Pros
- Comprehensive platform covering experiment tracking, model registry, LLMOps, and agent observability
- Weave provides deep, agent-native tracing and built-in signals for production monitoring
- Free tier available for personal development and academic research
- Supports both cloud-hosted and privately-hosted deployments for security and compliance
- Flexible evaluation framework that integrates with production traces and autonomous iteration
- Strong community support and extensive documentation
Cons
- Free tier is restricted to personal or academic use, not for corporations
- Free plan has limited storage (5 GB) and Weave data ingestion (1 GB/month)
- Pro plan is capped at teams under 50 employees; larger teams must upgrade to Enterprise
- Enterprise pricing is custom and may be expensive for small organizations
- Some advanced features (HIPAA, single-tenant, custom roles) are only available in Enterprise
Best For
Building and iterating on production AI agents with continuous reliability improvementMonitoring multi-turn, multi-agent systems to surface failure modes and root causesEvaluating and comparing LLM prompts, models, and fine-tuned versions before deploymentSafeguarding AI applications with automated safety and quality checks in productionTracking and managing the entire ML lifecycle from experiment to deploymentCollaborating on model development and sharing results with team dashboards
FAQ
What is Weave in Weights & Biases?
Weave is an observability and continuous improvement tool for production AI agents. It provides end-to-end tracing, out-of-the-box signals to surface failure modes, a flexible evaluation framework, and the ability to connect coding agents like Claude Code for automatic iteration loops.
Does Weights & Biases have a free plan?
Yes, there is a Free plan at $0/month designed for personal development of AI applications and models. It includes experiment tracking, Weave tracing (with 1 GB/month data ingestion), model registry, and community support. Corporate use is not allowed on the free plan.
What types of guardrails does Weave offer?
Weave Guardrails include pre-built scorers for safety (toxicity, bias, PII detection, hallucinations) and quality (coherence, fluency, context relevance) to support responsible AI.