DeepEval vs Phoenix
Updated March 10, 2026
Overview
DeepEval is an open-source LLM evaluation framework built for unit testing AI outputs. It provides 14+ evaluation metrics including hallucination detection, answer relevancy, and contextual recall. Integrates with pytest, supports custom metrics, and works with any LLM provider for automated quality assurance in CI/CD pipelines.
Phoenix is an open-source LLM observability and evaluation platform from Arize AI. It supports OpenTelemetry-based tracing across LLM and agent applications, with built-in evaluators, dataset management, and prompt playgrounds. Phoenix can be self-hosted with Docker or run via the Arize-hosted cloud version.
Key features
Core capabilities each platform advertises.
- OpenTelemetry-based LLM and agent tracing
- Built-in evaluators for hallucination and relevance
- Dataset and experiment management
- Prompt playgrounds and versioning
- Self-hosted Docker deployment or Arize cloud
Strengths and tradeoffs
What each tool does well, and the limitations to keep in mind.
Pros
- Open-source
- Comprehensive metrics
Cons
- Manual setup
Pros
- Open-source with active development by Arize
- OpenTelemetry-native (no proprietary trace format lock-in)
- Strong evaluator library out of the box
- Both self-hosted and managed cloud options available
- Upgrade path to full Arize enterprise platform
Cons
- Smaller community than Langfuse for open-source-first teams
- Cloud version's enterprise pricing is contact-sales only
- UI and feature set tilt toward ML engineers more than application developers
DeepEval or Phoenix — which should you choose?
Choose DeepEval if you wantChoose if you want
Choose Phoenix if you wantChoose if you want
- OpenTelemetry-native LLM observability
- Hallucination detection for RAG
- Experiment tracking and golden-set evaluation
- Prompt iteration and comparison
- Self-hosted tracing for compliance-sensitive teams
Compare DeepEval and Phoenix on your own traffic
Respan lets you trace LLM and agent calls across any model or framework, A/B test prompts on production traffic, and route requests across 500+ models through one gateway.