What is Arize Phoenix?
Arize Phoenix is an open-source observability and evaluation tool for LLM applications and AI agents. It records traces of the steps a request passes through (retrieval, tool calls, model responses), so you can see where a workflow broke. It is built on the OpenInference specification and OpenTelemetry instrumentation.
You can start it locally with a single command (uvx arize-phoenix serve) or self-host it in your own environment. With it you can run evaluations, for example using one LLM to judge another for relevance, toxicity or response quality, run experiments and compare results, and annotate data. The managed version, Arize AX, adds SaaS and enterprise options.
Key features
- Tracing of LLM requests and agent steps
- LLM-based evaluations for relevance, toxicity and quality
- Experiments and result comparison
- Human annotations and labeling queues
- Local run or self-hosting
- OpenTelemetry and OpenInference instrumentation
Who is it for
- AI engineers
- Developers building LLM applications
- Data science teams
- Companies that need self-hosted observability
Pros and cons
- Open source and free to self-host
- Easy local start with one command
- Integrates with existing OpenTelemetry tooling
- Paid tiers for the managed AX version are priced separately
Arize Phoenix pricing
| Plan | Price | Includes |
|---|---|---|
| AX Free | 0 USD / month | 10 issues per month, 25k trace spans per month, 1 GB ingestion, 15 days retention, SaaS |
| AX Pro | 50 USD / month | 25 issues per month, 50k trace spans per month, 10 GB ingestion, 30 days retention, SaaS |
Prices copied from Arize Phoenix pricing, checked October 12, 2026. Currency as shown by the vendor; taxes may apply.
Arize Phoenix pricing details →
Is Arize Phoenix free?
Yes, there is a free plan. Phoenix OSS is open source and can be run locally or self-hosted. AX Free includes 25k spans per month, 1 GB ingestion and 15 days retention, with unlimited users and evals.
Arize Phoenix alternatives
| Tool | Price from | Free plan | Category |
|---|---|---|---|
 Groq | not listed | ? | APIs & models |
 Google AI Studio | 0,75 USD | ? | APIs & models |
 OpenAI Platform | 0,10 USD | ? | APIs & models |
 Helicone | 79 USD/mo | yes | APIs & models |
 LLM | not listed | yes | APIs & models |
 Cartesia | 5 USD/mo | yes | APIs & models |
All alternatives to Arize Phoenix →
FAQ
What is Arize Phoenix used for?
Open-source tool for tracing, evaluating and debugging LLM apps and AI agents, for developers who want to self-host.
Is Arize Phoenix free?
Yes, there is a free plan. Phoenix OSS is open source and can be run locally or self-hosted. AX Free includes 25k spans per month, 1 GB ingestion and 15 days retention, with unlimited users and evals.
How much does Arize Phoenix cost?
The cheapest paid plan is 50 USD/mo (vendor pricing, October 12, 2026).
What are the best Arize Phoenix alternatives?
Closest alternatives: Groq, Google AI Studio, OpenAI Platform, Helicone, LLM.
Data checked October 12, 2026 on the vendor website (phoenix.arize.com).