companies

Arize AI

AI observability and evaluation company behind Arize AX and the open-source Phoenix project for tracing and evaluating LLM apps.

Arize AI was founded in 2020 by Jason Lopatecki and Aparna Dhinakaran, who had worked together at TubeMogul and saw the same gap repeatedly at Uber and other ML-heavy companies: teams could train a model but had almost no visibility into how it behaved once it hit production traffic. The company started in classical ML monitoring - drift detection, performance degradation, embedding analysis - and expanded into large language model and agent observability as those workloads became the dominant thing teams needed to debug. Its open-source project, Phoenix, has become one of the more widely adopted tracing and evaluation libraries for LLM applications, built on OpenTelemetry so it works across frameworks like LangChain, LlamaIndex, and CrewAI without vendor lock-in. Arize AX is the commercial platform built on the same foundations, adding hosted tracing, LLM-as-judge evaluation, prompt management, and an AI debugging assistant called Alyx. The company raised a $70 million Series C in February 2025 led by Adams Street Partners, with Microsoft's M12 and Datadog among its investors, bringing total funding to roughly $131 million.

Founded

2020

Headquarters

Berkeley, United States

Sector

infrastructure