Arize Phoenix vs OpenLIT
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.
OpenLIT
Apache-2.0 OpenTelemetry-native platform covering LLM tracing, evals, prompts, guardrails and a Vault - plus the one thing nearly every competitor ignores entirely, GPU monitoring for self-hosted inference.
| Arize Phoenix | OpenLIT | |
|---|---|---|
| Category | Observability & Tracing | Observability & Tracing |
| Our rating | 4/5 | 4/5 |
| Starting price | $0 | $0 (Apache 2.0) |
| Billing meter | No usage metering | No usage metering |
| Free plan | Yes | Yes |
| Free self-hosting | Yes, free | Yes, free |
| Best for | Teams that want fast, framework-agnostic OSS tracing and strong RAG eval, and who are not reselling Phoenix as a hosted service | Teams running self-hosted inference on their own GPUs, where correlating GPU health with model performance matters. Also a strong free choice for anyone wanting broad AI engineering tooling in one Apache-2.0 package. |
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 OpenLIT
OpenLIT is the only tool in this category that takes the GPU layer seriously, and if you run your own inference that alone may decide it. Its OpenTelemetry GPU collector exports utilisation, memory, temperature and power as standard OTel signals, so you can correlate a latency regression with thermal throttling or a KV cache leak in the same dashboard - a class of problem that is completely invisible to Langfuse, LangSmith or Braintrust, because they assume you call an API. Beyond that it is unusually broad for a free tool - Apache 2.0 across the core, covering observability, evals, guardrails, prompt management, a Vault and a Playground. The trade-off is breadth over depth, since each module is lighter than a dedicated competitor, and the community is small at roughly 2,500 stars. Two things we could not resolve - an enterprise eBPF controller is referenced without clear licensing terms, and the project has recently described itself as a Harness Engineering platform without public explanation of what that means.
Full OpenLIT review →Frequently Asked Questions
What is the main difference between Arize Phoenix and OpenLIT?
Arize Phoenix: Teams that want fast, framework-agnostic OSS tracing and strong RAG eval, and who are not reselling Phoenix as a hosted service OpenLIT: Teams running self-hosted inference on their own GPUs, where correlating GPU health with model performance matters. Also a strong free choice for anyone wanting broad AI engineering tooling in one Apache-2.0 package. 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 OpenLIT?
It depends entirely on your workload shape, because they meter differently - Arize Phoenix bills on no usage metering and OpenLIT bills on no usage metering. Published starting prices are $0 and $0 (Apache 2.0) 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 OpenLIT?
Arize Phoenix: Yes, free. OpenLIT: Yes, free. Free self-hosting means no licence fee, not no cost - you still own the infrastructure, upgrades and on-call.