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Arize Phoenix vs Braintrust: catalog facts
Arize Phoenix	Braintrust
Freemium Phoenix is free to self-host; Arize AX is a separate managed paid platform.	Freemium Self-serve sign-up with paid plans listed on the pricing page.
Web, Self-hosted	Web
Tracing, evals, prompts and experiments in one tool Runs locally, in Docker or on Kubernetes	Real-time tracing of prompts, responses and tool calls Evals scored by LLMs, code or humans
Source-available license rather than an OSI-approved one Some advanced features are in the separate paid Arize AX product	Hosted service that requires an account Aimed at teams building LLM products, not individual users
Self-hosted, Hosted service	Hosted service
Closed source	Closed source
License: Elastic-2.0	License not stated
Not stated if an account is needed	Account needed
Not stated if it works offline	Needs internet
Official website Full listing and sources Checked September 26, 2026	Official website Full listing and sources Checked October 1, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.