Langfuse vs Arize AX 2026: Two Free Tiers, Two Very Different Paid Steps
Quick verdict: Langfuse is our overall pick for langfuse vs arize-ax.
Langfuse: free at 50K units, then $29/mo for 100K units with 90-day retention and unlimited users. Arize AX: free at 25K spans and 1 GB, then $50/mo for 50K spans and 10 GB with unlimited users and evals.
| Tool | Rating | Pricing | Best for |
|---|---|---|---|
| Langfuse Best overall Best for teams | 4.3/5 | Free $29/mo (Core) | Langfuse is the open-source-first LLM observability platform: free Hobby with 50K units a … |
| Arize AX Best free | 4.0/5 | Free $50/mo (AX Pro) | Arize AX is the cheapest paid step in the cluster at $50/mo, with a $0 Free tier (25K span… |
Bottom line: Langfuse for cloud-first teams that want a deeper free tier and a lower first paid step, plus documented discounts and self-hosting as a supported path. Arize AX if unlimited evaluations and unlimited users at $50/mo are the deciding factors, or if you want the free open-source Phoenix for local work. Both are strong value; Langfuse wins the entry price and retention on Core, Arize wins the seat and eval model. Pick Braintrust only if per-score pricing is what you need to forecast.
Pricing and details
Langfuse · 4.3/5
Free plan available · $29/mo (Core)
Usage is billed in units (100K units included on paid tiers, then $8 per additional 100K, lower at volume); a separate self-hosted pricing page exists for on-prem deployments
No published annual rate; Pro carries an optional Teams add-on at $300/mo for SSO, SSO enforcement and fine-grained RBAC
Langfuse is the open-source-first LLM observability platform: free Hobby with 50K units a month, Core at $29/mo for 100K units and 90-day retention, Pro at $199/mo with three-year retention, Enterprise at $2,499/mo.
Score breakdown
Pros
- A real free tier with no credit card: 50K units a month, all platform features, 30 days of data access and 2 users
- Core at $29/mo is by far the cheapest paid step in the cluster, with unlimited users on every paid tier
- Cloud and self-hosted deployment from the same product, so privacy-sensitive teams have a real path instead of a sales call
- Published discounts for startups, research and students, plus a documented open-source project track
Cons
- Core retains data for 90 days only - three-year retention needs the $199 Pro plan
- No deployment runtime or autonomous debugging engine, so it covers tracing and evaluation but not the agent platform around them
- The optional Teams add-on for SSO and fine-grained RBAC is another $300/mo on top of Pro
Pricing verified 2026-10-03
Arize AX · 4.0/5
Free plan available · $50/mo (AX Pro)
Billed on signals, spans, ingestion volume and retention rather than seats - users and evals are unlimited on every tier; self-hosted deployment is Enterprise-only, while the open-source Phoenix platform is free and local
No published annual rate; a separate startup pricing track exists on the pricing page
Arize AX is the cheapest paid step in the cluster at $50/mo, with a $0 Free tier (25K spans, 1 GB, 15-day retention) and a free open-source sibling in Arize Phoenix for fully local tracing.
Score breakdown
Pros
- Unlimited users and unlimited evaluations on every tier, including the free one - the only cluster member that never charges for seats
- $50/mo is the cheapest paid step in the set, undercutting Braintrust Pro by 5x
- Arize Phoenix is a genuinely free, open-source, local-first platform for tracing and evaluation with no account required
- Session-level and multi-modal tracing (image, voice, PDF), agent trajectory visualizations and online/offline evals are unlimited on all tiers
Cons
- The free tier is narrow - 10 signals a month and 25K spans, so production volume will not fit
- Self-hosted deployment is Enterprise-only; the free local option is the separate Phoenix project, not AX itself
- SOC 2 Type II, SSO, audit logs, HIPAA and data-region choice start at Enterprise
Pricing verified 2026-10-03
Frequently asked questions
Which is better overall, Langfuse or Arize AX?
Langfuse is our overall pick (4.3/5 vs 4.0/5). Langfuse: free at 50K units, then $29/mo for 100K units with 90-day retention and unlimited users. Arize AX: free at 25K spans and 1 GB, then $50/mo for 50K spans and 10 GB with unlimited users and evals.
Do Langfuse and Arize AX offer free plans?
Langfuse and Arize AX have a free tier. Langfuse paid plans start at $29/mo (Core); Arize AX paid plans start at $50/mo (AX Pro).
What does Langfuse cost?
$29/mo (Core) — Usage is billed in units (100K units included on paid tiers, then $8 per additional 100K, lower at volume); a separate self-hosted pricing page exists for on-prem deployments. Prices were last verified on 2026-10-03.