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Opik (Comet) vs Arize Phoenix
Quick verdict
Key difference: Arize Phoenix is OpenTelemetry-native (no lock-in) while Opik (Comet) uses a proprietary SDK.
Side-by-side comparison from the Agent Observability Index: licensing, self-hosting, pricing model and integrations — no vendor copy, primary sources linked.
| Opik (Comet) | Arize Phoenix | |
|---|---|---|
| One-liner | Open-source LLM evaluation and tracing platform from Comet, combining trace logging, eval metrics and CI-friendly test suites. | Open-source, OpenTelemetry-based tracing and evaluation library that runs locally or self-hosted, serving as the OSS on-ramp to Arize's enterprise platform. |
| Category | Observability & Tracing | Observability & Tracing |
| OpenTelemetry-native | No | Yes |
| Open source | Yes | Yes |
| Self-hostable | Yes | Yes |
| Pricing model | freemium | free |
| Pricing notes | Apache-2.0 self-host free; Comet cloud free tier + paid plans | Fully free OSS (Elastic License v2); hosted Phoenix Cloud has a free tier |
| Frameworks | openai-sdk, langchain, llamaindex, litellm, dspy, haystack | openai-sdk, langchain, llamaindex, dspy, opentelemetry, smolagents |
| GitHub stars | 19.6k | 10.1k |
| Maturity (GitHub signal) | 100/100 (Mature) | 90/100 (Mature) |
| Funding / ownership | Backed by Comet ML ($50M Series B, 2021) | Backed by Arize AI ($70M Series C, Feb 2025) |
How to choose
- Both link to primary pricing sources below — verify current tiers before committing; this market shifts monthly.
Sources: Opik (Comet) · Arize Phoenix
Frequently asked questions
Is Opik (Comet) or Arize Phoenix open source?
Opik (Comet): Yes. Arize Phoenix: Yes.
Can Opik (Comet) and Arize Phoenix be self-hosted?
Opik (Comet): Yes. Arize Phoenix: Yes.
Opik (Comet) vs Arize Phoenix: which should I choose?
Key difference: Arize Phoenix is OpenTelemetry-native (no lock-in) while Opik (Comet) uses a proprietary SDK.