Arize Phoenix vs PromptLayer

Arize Phoenix is free, open-source software for tracing, evaluating, debugging, and improving AI applications. It captures model calls, retrieval, tool use, and custom logic as OpenTelemetry traces. Teams can score traces and spans with LLM evaluators, code checks, or human labels. Prompt tools provide versioning, side-by-side testing, and call replay, while dataset experiments compare evaluation results across application versions. Documented integrations include LlamaIndex, LangChain, DSPy, OpenAI, Bedrock, and Anthropic, plus evaluation libraries such as Harbor, Ragas, Cleanlab, and MLflow. Phoenix runs locally or can be self-hosted with Docker, Kubernetes, or a cloud environment; Arize says self-hosting keeps traces in the user’s environment. Self-hosted authentication supports OAuth2 identity providers with an OpenID Connect well-known endpoint. The Phoenix plan costs nothing and leaves trace spans, ingestion, projects, and retention under user management. The project is ELv2 licensed and built by Arize AI and the open-source community.

PromptLayer combines a prompt registry and visual prompt CMS with evaluations, observability, and agent tracing for teams building AI products. Teams can visually edit, version, test, and deploy prompts without waiting for an application redeploy, allowing domain experts and non-technical stakeholders to work alongside engineers. Evaluations can run when prompt versions change, through the API, or on demand in the UI. They include historical backtests and side-by-side model comparisons. Tracking covers requests, traces, cost, latency, token usage, scores, and custom metadata, with OpenTelemetry span support. The OpenAI integration includes versioned prompts, release labels, request observability, evaluations, and model comparisons. Free, Pro, and Team are cloud-hosted in the US; Enterprise offers self-hosting on GCP, AWS, or Azure, EU cloud hosting, or single-tenant cloud hosting. PromptLayer states that it maintains SOC 2 Type 2, HIPAA, GDPR, and CCPA compliance. Free costs nothing, Pro costs $49 a month, and Team costs $500 a month. Enterprise pricing is custom.