Arize Phoenix vs Galileo
Both are observability & tracing tools. Here is how they actually differ on price, billing model and deployment.
Arize Phoenix
The default open-source choice for LLM tracing and eval - runs locally in under a minute, built on OpenTelemetry. The catch is the license - the server is Elastic License 2.0, source-available, not OSI open source.
Galileo
The best-funded evaluation-and-observability platform in this space, built around proprietary Luna eval models. Not to be confused with the Google-acquired text-to-UI tool of the same name. Real pricing is sales-led above $100/mo.
| Arize Phoenix | Galileo | |
|---|---|---|
| Category | Observability & Tracing | Observability & Tracing |
| Our rating | 4/5 | 4/5 |
| Starting price | $0 | $100/mo |
| Billing meter | No usage metering | span |
| Free plan | Yes | Yes |
| Free self-hosting | Yes, free | No or paid tier only |
| Best for | Teams that want fast, framework-agnostic OSS tracing and strong RAG eval, and who are not reselling Phoenix as a hosted service | Enterprise GenAI teams that have been burned by production hallucinations and want research-grade eval metrics plus guardrails, and can run a sales process |
Our verdict on Arize Phoenix
The default open-source pick for good reasons - it starts in under a minute, the RAG eval is the best around, and it is built on OpenTelemetry so you are not locked to one framework. Just read the license before you build a business on it. The server is Elastic License 2.0, source-available rather than OSI open source, which only bites if you plan to offer Phoenix as a service - but it is not what "fully open source" implies.
Full Arize Phoenix review →Our verdict on Galileo
Galileo is the best-funded and arguably most research-forward platform here, and the Luna eval models are a real bet on making evaluation cheap enough to run continuously. Two caveats. First, make sure you're evaluating this Galileo and not the design tool that shares the name - the pricing and reviews get conflated constantly. Second, above the $100 Pro tier everything is contact-sales, and self-host is Enterprise-only, so this is a platform you buy through a rep, not a card.
Full Galileo review →Frequently Asked Questions
What is the main difference between Arize Phoenix and Galileo?
Arize Phoenix: Teams that want fast, framework-agnostic OSS tracing and strong RAG eval, and who are not reselling Phoenix as a hosted service Galileo: Enterprise GenAI teams that have been burned by production hallucinations and want research-grade eval metrics plus guardrails, and can run a sales process Both sit in Observability & Tracing, so the decision usually comes down to billing model and deployment rather than raw capability.
Which is cheaper, Arize Phoenix or Galileo?
It depends entirely on your workload shape, because they meter differently - Arize Phoenix bills on no usage metering and Galileo bills on span. Published starting prices are $0 and $100/mo respectively, but those numbers are not comparable until you apply them to the same traffic. Use our cost calculator to model both against your own request volume and span count.
Can I self-host Arize Phoenix or Galileo?
Arize Phoenix: Yes, free. Galileo: No or paid tier only. Free self-hosting means no licence fee, not no cost - you still own the infrastructure, upgrades and on-call.