MLflowSelf-hosted (open source)$0/moWithin the free allowanceFree and open source; running the tracking server is your cost. Managed versions from Databricks and cloud providers are priced by those vendors and not modeled.
LLM Observability & Evals pricing, compared
Pick a scale or set your usage. Each tool shows its cheapest plan for it, cheapest first, with the arithmetic and the vendor's pricing page. Price is one input — which one fits your situation matters as much.
Tools priced6checked since 2026-10-03
With a free plan5of 6
Side project$0 – $25a month
Growing$0 – $475a month
Scaling$0 – $24,975a month
5 of 6 tools fit this usageList prices, USD per month
MLflowSelf-hosted (open source)$0/moWithin the free allowance
OpikPro Cloud$19/mo$19 planOpik prices by spans (treated as traces here; a trace usually has several spans). Pro overage is $5 per 100k spans. Free allows up to 10 team members and Pro up to 50. The Apache-licensed version is free to self-host (hosting costs are yours).
LangfuseCore$29/mo$29 planLangfuse bills "units" — every trace, observation (span, event, generation) and score counts as one — so a trace with several steps uses several units; the model treats units as traces. Overage is graduated ($8 per 100k up to 1M, $7 to 10M, $6.50 to 50M, $6 above); the first tier is modeled. Hobby has 2 users and 30 days of data; Pro adds 3-year retention. Self-hosting the open-source version is free (hosting costs are yours).
HeliconePro$116/mo$114 plan + 10k traces × $0.175 per 1,000 tracesBilled per logged request (treated as a trace). Graduated rates on Pro ($79/mo, 10k included) — $0.0007 to 30k, $0.00035 to 90k, $0.000175 to 250k, $0.0000875 to 800k, $0.00004375 to 2.5M, $0.00002 beyond. Team ($799/mo) has the same rates and more features. Storage beyond 1 GB is billed separately.
LangSmithDeveloper$475/mo95k traces × $0.005 per traceExtra base traces (14-day retention) cost 0.005 LSU each at $1 per LSU; upgrading a trace to 180-day extended retention adds 0.0025 LSU. Developer is limited to 1 seat; Plus is $39 per seat per month (one seat modeled) with 10k traces included in total. Deployments, Fleet and sandboxes are metered separately.
Arize PhoenixOver every plan's limits—/moArize prices by spans (treated as traces here; a trace usually has several spans). The page lists no overage price, so each plan is modeled as capped at its included spans; above 50k spans/month is Enterprise (custom pricing). Ingestion is also limited (1 GB Free, 10 GB Pro). Phoenix itself is open source and free to self-host (hosting costs are yours).
Read from each vendor's pricing page (oldest check 2026-10-03). The model is plan fee + usage beyond what's included × the vendor's rate; volume discounts, annual billing, taxes and regional prices are left out — see each tool's notes. Always confirm on the vendor's page before you commit.
Cost as you grow
Each tool's cheapest usable plan as the product grows.
At three scales
| Tool | Side projecttraces 10k traces | Growingtraces 100k traces | Scalingtraces 5M traces |
|---|---|---|---|
| MLflow | $0Self-hosted (open source) | $0Self-hosted (open source) | $0Self-hosted (open source) |
| Opik | $0Free Cloud | $19Pro Cloud | $264Pro Cloud |
| Langfuse | $0Hobby | $29Core | $421Core |
| Helicone | $0Hobby | $116Pro | $315Pro |
| LangSmith | $25Developer | $475Developer | $24,975Developer |
| Arize Phoenix | $0AX Free | —over limits | —over limits |
Every plan
What each LLM observability & evals plan costs, includes and caps, as modelled here.
MLflowFree and open source under Apache 2.0; running the tracking server is your only cost.
| Plan | Monthly fee |
|---|---|
| Self-hosted (open source) | Free |
Free and open source; running the tracking server is your cost. Managed versions from Databricks and cloud providers are priced by those vendors and not modeled.
Checked 2026-10-03 · pricing page ↗ · MLflow pricing in full →OpikOpik Cloud is free for 25k spans a month; Pro is $19 per month with 100k spans, then $5 per 100k spans.
| Plan | Monthly fee | Traces per month |
|---|---|---|
| Free Cloud | Free | 25k traces includedup to 25k traces |
| Pro Cloud | $19/mo | 100k traces includedthen $0.05 per 1,000 traces |
Opik prices by spans (treated as traces here; a trace usually has several spans). Pro overage is $5 per 100k spans. Free allows up to 10 team members and Pro up to 50. The Apache-licensed version is free to self-host (hosting costs are yours).
Checked 2026-10-03 · pricing page ↗ · Opik pricing in full →LangfuseFree for 50k units a month; Core is $29 and Pro $199 per month, each with 100k units, then $8 per 100k units, cheaper at volume.
| Plan | Monthly fee | Traces per month |
|---|---|---|
| Hobby | Free | 50k traces includedup to 50k traces |
| Core | $29/mo | 100k traces includedthen $0.08 per 1,000 traces |
| Pro | $199/mo | 100k traces includedthen $0.08 per 1,000 traces |
Langfuse bills "units" — every trace, observation (span, event, generation) and score counts as one — so a trace with several steps uses several units; the model treats units as traces. Overage is graduated ($8 per 100k up to 1M, $7 to 10M, $6.50 to 50M, $6 above); the first tier is modeled. Hobby has 2 users and 30 days of data; Pro adds 3-year retention. Self-hosting the open-source version is free (hosting costs are yours).
Checked 2026-10-03 · pricing page ↗ · Langfuse pricing in full →HeliconeFree for 10,000 requests a month; Pro is $79 per month with 10,000 requests included, then graduated per-request rates from $0.0007 down to $0.00002.
| Plan | Monthly fee | Traces per month |
|---|---|---|
| Hobby | Free | 10k traces includedup to 10k traces |
| Pro | $79/mo | 10k traces includedthen $0.7 per 1,000 traces |
| ↳ next tier | 30k traces includedthen $0.35 per 1,000 traces | |
| ↳ next tier | 90k traces includedthen $0.175 per 1,000 traces | |
| ↳ next tier | 250k traces includedthen $0.0875 per 1,000 traces | |
| ↳ next tier | 800k traces includedthen $0.04375 per 1,000 traces | |
| ↳ next tier | 2.5M traces includedthen $0.02 per 1,000 traces |
Billed per logged request (treated as a trace). Graduated rates on Pro ($79/mo, 10k included) — $0.0007 to 30k, $0.00035 to 90k, $0.000175 to 250k, $0.0000875 to 800k, $0.00004375 to 2.5M, $0.00002 beyond. Team ($799/mo) has the same rates and more features. Storage beyond 1 GB is billed separately.
Checked 2026-10-03 · pricing page ↗ · Helicone pricing in full →LangSmithFree for one seat with 5k base traces a month; Plus is $39 per seat per month with 10k traces, then $0.005 per extra base trace.
| Plan | Monthly fee | Traces per month |
|---|---|---|
| Developer | None | 5k traces includedthen $0.005 per trace |
| Plus | $39/mo | 10k traces includedthen $0.005 per trace |
Extra base traces (14-day retention) cost 0.005 LSU each at $1 per LSU; upgrading a trace to 180-day extended retention adds 0.0025 LSU. Developer is limited to 1 seat; Plus is $39 per seat per month (one seat modeled) with 10k traces included in total. Deployments, Fleet and sandboxes are metered separately.
Checked 2026-10-03 · pricing page ↗ · LangSmith pricing in full →Arize PhoenixArize AX is free for 25k spans a month and $50 per month for 50k spans on Pro; Phoenix is free to self-host.
| Plan | Monthly fee | Traces per month |
|---|---|---|
| AX Free | Free | 25k traces includedup to 25k traces |
| AX Pro | $50/mo | 50k traces includedup to 50k traces |
Arize prices by spans (treated as traces here; a trace usually has several spans). The page lists no overage price, so each plan is modeled as capped at its included spans; above 50k spans/month is Enterprise (custom pricing). Ingestion is also limited (1 GB Free, 10 GB Pro). Phoenix itself is open source and free to self-host (hosting costs are yours).
Checked 2026-10-03 · pricing page ↗ · Arize Phoenix pricing in full →