OpenLLMetry vs Phoenix (Arize)
Both are alternatives to LangSmith. Here's how they stack up — verified facts, no spin.
Also searched as Phoenix (Arize) vs OpenLLMetry — same comparison, one verdict.
OpenLLMetry
Apache-2.0 OpenTelemetry instrumentation — send traces anywhere you already send them.
OpenLLMetry takes the opposite approach to a platform: it is a set of Apache-2.0 OpenTelemetry extensions that emit LLM traces in a standard format, so they flow into whatever you already run — Grafana, Datadog, Honeycomb, Jaeger or Traceloop's own hosted backend. If you already have observability infrastructure, this adds LLM visibility to it rather than asking you to adopt a second, parallel system. It is also the strongest hedge against lock-in: standard telemetry moves between backends by configuration.
Phoenix (Arize)
Strong evaluation tooling — but read the licence before you build on it.
Phoenix is Arize's tracing and evaluation tool, and its evaluation workflow is among the best available: run experiments, score outputs against datasets, and inspect where a chain went wrong. It runs locally in a notebook or as a self-hosted service. The critical detail most listicles omit is the licence — Phoenix is Elastic License 2.0, which is source-available rather than open source. You may use and modify it, but you may not offer it to third parties as a hosted or managed service, and you may not circumvent its licence-key functionality.
Side by side
| OpenLLMetry | Phoenix (Arize) | |
|---|---|---|
| Sovereignty Score | 92 | 62 |
| Open source | Yes | No |
| Self-hostable | Yes | Yes |
| Local-first | Yes | Yes |
| License | Apache-2.0 | Elastic License 2.0 (source-available, not OSI open source) |
| Pricing | Free — Apache-2.0 instrumentation libraries. You pay only whatever backend you already send telemetry to; a hosted Traceloop backend is available separately. | Free to self-host under ELv2 for your own internal use. Arize's commercial platform is priced separately. |
OpenLLMetry edges it on the Sovereignty Score, but the right pick depends on the trade-offs below.
OpenLLMetry
Strengths
- +Apache-2.0 throughout — no enterprise-directory carve-out
- +Standard OpenTelemetry: traces go to a backend you already operate
- +The best protection against lock-in — switching backends is configuration
- +Reuses your existing observability stack instead of adding a parallel one
Trade-offs
- −Instrumentation, not a platform — no evaluation or prompt-management UI
- −You need a trace backend already, or you are choosing one anyway
- −Generic backends render LLM traces less legibly than a purpose-built UI
- −Smaller project (about 7k stars) than Langfuse
Phoenix (Arize)
Strengths
- +Excellent evaluation and experiment tooling — the strongest of this group
- +Runs locally, including straight from a notebook
- +Self-hostable, so traces stay in your infrastructure
- +Actively developed, with commits landing daily
Trade-offs
- −Elastic License 2.0 — source-available, NOT open source; you cannot offer it as a managed service
- −The licence restriction is a real constraint if your product is itself a platform
- −Score of 62 reflects the licensing limitation, not the engineering quality
- −Smaller community than Langfuse
Related alternative guides
Facts verified 2026-07-30. Licenses and pricing change — spotted something out of date? That's a correction we want.