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Head-to-head · LLM Observability Tools

Arize Phoenix vs W&B Weave

  • Updated Oct 2026
  • Both researched from official sources
  • 7 checks side by side
Higher score Arize Phoenix #3 in LLM Observability Tools 9.2/10 Free plan Free plan✓ 6 of 6 features Visit Arize Phoenix
W&B Weave #5 in LLM Observability Tools 9.0/10 Free plan · 30-day trial Free planFree trial✓ 6 of 6 features Visit W&B Weave

Arize Phoenix leads on 0 checks, W&B Weave on 0, and 7 are even. Who comes out ahead on the 7 yes/no, price and count checks where we have data for both products. The editor score weighs everything else too.

Our verdict

  • Highest scoreArize Phoenix · 9.2/10
  • Free planboth
  • Free trialonly W&B Weave

Arize Phoenix scores higher on our rubric for llm observability tools: 9.2 against 9.0 out of 10; our editors rank them #3 and #5.

Arize Phoenix is the better fit for developers wanting free open-source LLM observability. W&B Weave is the better fit for growing teams wanting mature, broad observability.

  • Arize Phoenix fits best

    Developers wanting free open-source LLM observability

  • W&B Weave fits best

    Growing teams wanting mature, broad observability

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Side by side

Feature Arize Phoenix 9.2/10 Visit ↗ W&B Weave 9.0/10 Visit ↗
At a glance
Editor score 9.2 9.0
Ranking #3 in LLM Observability Tools #5 in LLM Observability Tools
Best for Developers wanting free open-source LLM observability Growing teams wanting mature, broad observability
Pricing model Free Free plan + paid
Starting price Free $60/mo
Free plan ✓ ✓
Free trial — 30 days
Deployment Cloud, Self-hosted Cloud, Self-hosted
Platforms Web Web
Support Community, Docs Email, Live chat, Community, Docs
Integrations 11 integrations 30+ integrations
Built for Solo, Small business, Mid-market, Enterprise Small business, Mid-market, Enterprise
Features Arize Phoenix 6/6 · W&B Weave 6/6
LLM tracing ✓ ✓
LLM evaluations ✓ ✓
Prompt management ✓ ✓
Agent tracing ✓ ✓
Retrieval tracing ✓ ✓
Token cost tracking ✓ ✓
Specs
Deployment options Both Both
Our review
Pros
  • Free open-source plan with tracing, evaluations, and prompt iteration
  • Tracks retrieval, tool use, prompts, experiments, and token-based costs
  • Supports web, API, self-hosted deployment and multiple AI frameworks
  • Detailed tracing for LLM calls, agents, RAG steps, costs, and latency
  • Evaluations, scorers, prompt versioning, and experimentation in one platform
  • Web, API, and self-hosted deployment with broad framework integrations
Cons
  • Focused on AI applications and agents rather than general observability
  • Instrumentation coverage centers on Python, TypeScript, and Java
  • Hosted Phoenix Cloud is distinct from local-first and self-hosted use
  • Weave data ingestion, storage, and some usage are billed separately
  • The Free plan has community support rather than priority support
  • Its broad feature set may exceed the needs of teams seeking simple tracing
Our verdict

Arize Phoenix is an open-source observability and evaluation platform for AI applications and agents. It is designed for developers who need visibility into model calls, retrieval, tool use, and custom application logic. The platform…

Read the review →

W&B Weave is an observability and evaluation platform for teams building LLM applications and production agents. It records inputs, outputs, metadata, latency, token usage, costs, tool calls, and multi-step agent activity. The platform…

Read the review →
  1. Arize PhoenixLLM Observability Tools 9.2Free plan
  2. W&B WeaveLLM Observability Tools 9.0Free plan · 30-day trial

Strengths and trade-offs

  • Arize Phoenix — where it wins

    • Free open-source plan with tracing, evaluations, and prompt iteration
    • Tracks retrieval, tool use, prompts, experiments, and token-based costs
    • Supports web, API, self-hosted deployment and multiple AI frameworks

    Where it doesn't

    • Focused on AI applications and agents rather than general observability
    • Instrumentation coverage centers on Python, TypeScript, and Java
    • Hosted Phoenix Cloud is distinct from local-first and self-hosted use

  • W&B Weave — where it wins

    • Detailed tracing for LLM calls, agents, RAG steps, costs, and latency
    • Evaluations, scorers, prompt versioning, and experimentation in one platform
    • Web, API, and self-hosted deployment with broad framework integrations

    Where it doesn't

    • Weave data ingestion, storage, and some usage are billed separately
    • The Free plan has community support rather than priority support
    • Its broad feature set may exceed the needs of teams seeking simple tracing

More comparisons

All LLM observability tools comparisons → · Full ranking →

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

Last updated · How we research and update