Opik vs Arize Phoenix
Both are observability & tracing tools. Here is how they actually differ on price, billing model and deployment.
Opik
Comet's open-source LLM observability and eval platform - the cheapest paid cloud in the category at $19/mo, and the most permissive OSS license. Apache-2.0, full feature set self-hosted, and the fastest-growing project of its peers.
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.
| Opik | Arize Phoenix | |
|---|---|---|
| Category | Observability & Tracing | Observability & Tracing |
| Our rating | 5/5 | 4/5 |
| Starting price | $19/mo | $0 |
| Billing meter | span | No usage metering |
| Free plan | Yes | Yes |
| Free self-hosting | Yes, free | Yes, free |
| Best for | Teams that want a genuinely feature-complete open-source observability platform, or the cheapest managed cloud, without a license or feature-gate catch | Teams that want fast, framework-agnostic OSS tracing and strong RAG eval, and who are not reselling Phoenix as a hosted service |
Our verdict on Opik
The most honest open-source deal in the category - Apache-2.0, the full feature set self-hosted with no gates, and if you want managed, the cheapest cloud tier here at $19/mo. It is also the fastest-growing project of its peers, which tells you the market agrees. The one real watch-out is per-seat pricing - it scales poorly as your team grows, and a few large-project users report UI slowdown.
Full Opik review →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 →Frequently Asked Questions
What is the main difference between Opik and Arize Phoenix?
Opik: Teams that want a genuinely feature-complete open-source observability platform, or the cheapest managed cloud, without a license or feature-gate catch Arize Phoenix: Teams that want fast, framework-agnostic OSS tracing and strong RAG eval, and who are not reselling Phoenix as a hosted service Both sit in Observability & Tracing, so the decision usually comes down to billing model and deployment rather than raw capability.
Which is cheaper, Opik or Arize Phoenix?
It depends entirely on your workload shape, because they meter differently - Opik bills on span and Arize Phoenix bills on no usage metering. Published starting prices are $19/mo and $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 Opik or Arize Phoenix?
Opik: Yes, free. Arize Phoenix: Yes, free. Free self-hosting means no licence fee, not no cost - you still own the infrastructure, upgrades and on-call.