Arize AX and Phoenix review

Arize earns fourth place with two ways in. Phoenix is open source and can run locally or be self-hosted, which suits teams that want to start tracing without a vendor account. Arize AX is the hosted platform, and its pricing page lists OpenTelemetry compliant tracing, token, latency and cost tracking, online evals on traces and spans, trace evals for agent trajectories and session evals for multi-turn conversations, plus multi-modal tracing for image, voice and PDF. AX Free gives unlimited users, evals and experiments with 25k spans, 1 GB and 15 days of retention. AX Pro costs $50 a month for 50k spans, 10 GB and 30 days. Data can sit in the US, EU or Canada. Ease of use scores a little lower because teams have to choose between two products and move between them as needs grow, and self-hosted AX, SSO and audit logs all wait for Enterprise.

Who it is for

teams that want OpenTelemetry tracing with an open-source option

Price

AX Free with 25k spans a month; AX Pro $50 a month; Phoenix open source is free.

AX Pro For AI-native teams $50 per month
Quoted from the vendor pricing page on November 12, 2026.

Key features

• OpenTelemetry compliant tracing with token, latency and cost tracking
• Online evals on traces and spans, offline evals on datasets and experiments
• Trace evals for agent trajectories and session evals for multi-turn conversations
• Multi-modal tracing and evaluation for image, voice and PDF
• Phoenix can run locally or be self-hosted

Strengths and weaknesses

• Strength: Unlimited users, evals and experiments on the free AX plan
• Strength: AX Pro at $50 a month raises spans to 50k and storage to 10 GB
• Strength: Data regions in the US, EU or Canada
• Weakness: AX Free keeps data for only 15 days
• Weakness: Self-hosted AX deployment requires Enterprise
• Weakness: Enterprise SSO and audit logs are not in Free or Pro

Key facts

• Free plan: AX Free, 25k spans, 1 GB, 15-day retention
• AX Pro: $50 a month, 50k spans, 10 GB, 30-day retention
• Open source: Phoenix, run locally or self-host
• Data region: US, EU or CA

Where it ranks

Arize AX and Phoenix is No. 3 in our Best LLM Observability Tools verdict.