Promptfoo is the default pick for most readers because its Community edition is free forever and runs the same prompt across many models from one file, while Langfuse is the best hosted starting point at $29 a month and Comet Opik is the cheapest hosted entry at $19 a month. The free limits decide the shortlist more than the headline price: Langfuse Hobby allows 50,000 units a month, Arize AX Free allows 25,000 spans, and LangSmith Developer allows only 5,000 traces and one seat. Helicone is a special case: its hosted product stopped taking new signups after the Mintlify acquisition in March 2026, so new users should treat it as a self-hosted option only.
Picking a comparison platform starts with where your runs already live. If your prompts sit in code and CI, a test runner such as Promptfoo fits. If your models run in production, you need tracing, datasets, and experiment history, which points to Langfuse, LangSmith, Arize AX, Opik, or Braintrust. Free allowances here range from 5,000 traces a month to 50,000 units a month, so check the billing unit, the retention window, and the seat limit before you commit.
On this page
Best platforms to compare ai model results: comparison table
Swipe the table sideways on a phone to see every column.
| # | Name | Best for | Starting price | Free plan / trial | Link |
|---|---|---|---|---|---|
| 1 | Promptfoo | Developers running prompt and model tests from code | $0 per month | Yes | Visit |
| 2 | Comet Opik | Teams wanting a full open-source eval platform | $19 per month | Yes | Visit |
| 3 | Langfuse | Small teams needing hosted tracing and evals | $29 per month | Yes | Visit |
| 4 | LangSmith | Teams building on LangChain or LangGraph | $39 per seat per month | Yes | Visit |
| 5 | Arize Phoenix | OpenTelemetry teams comparing RAG and agent runs | $50 per month | Yes | Visit |
| 6 | W&B Weave | ML teams already using Weights and Biases | $60 per month | Yes | Visit |
| 7 | Helicone | Self-hosted request logging and cost tracking | $79 per month | Yes | Visit |
| 8 | Braintrust | Teams tracking eval quality across releases | $249 per month | Yes | Visit |
The 8 best best platforms to compare ai model results, in detail
Promptfoo
Best for: Developers running prompt and model tests from code
Promptfoo is a command-line tool that sends the same test inputs to different models or prompts, scores the outputs, and shows the results side by side. The Community edition is free forever and includes all eval features plus red teaming capped at 10,000 probes a month. The trade-off is that the free edition is a local tool.
- Centralized dashboards, team controls, monitoring, single sign-on, and an API sit in the Enterprise plan.
- OpenAI announced in March 2026 that it had agreed to acquire Promptfoo, and the project stays open source under the MIT license.
- Choose Promptfoo when your team is comfortable in the terminal.
- Skip it when non-technical reviewers need to browse results in a shared web view.
Pros
- Community edition is free forever under the MIT license
- one YAML file runs the same prompts across many providers
- red teaming is included
Cons
- No hosted team dashboard in the Community edition
- Enterprise and On-Premise prices are not published
Comet Opik
Best for: Teams wanting a full open-source eval platform
Opik is Comet’s open-source platform for tracing, evaluating, and monitoring LLM applications, RAG systems, and agents. The open-source edition costs $0 and includes the full backend. Free Cloud costs $0 for up to 10 team members, 25,000 spans a month, and 60-day retention.
- Pro Cloud costs $19 a month for up to 50 members and 100,000 spans, with extra spans at $5 per 100,000.
- Opik ships test suites for pass and fail checks, an Agent Playground, a prompt library, and an Agent Optimizer Online evaluation rules score productio
- Choose Opik for the whole platform free on your own servers, or the lowest hosted entry price in this list.
- Skip it when you need hosted single sign-on or role controls,
Pros
- Full backend is Apache 2.0 and free to self-host
- Pro Cloud costs $19 a month for 100,000 spans
- more than 30 built-in eval metrics
Cons
- Self-hosted build has no user management or logins
- single sign-on and role controls need the Enterprise plan
Langfuse
Best for: Small teams needing hosted tracing and evals
Langfuse is an open-source LLM observability platform with tracing, prompt management, datasets, experiments, and LLM-as-judge scoring. Langfuse Cloud has a free Hobby plan with 50,000 units a month, 30 days of data access, and 2 users. Core costs $29 a month with 100,000 units, 90 days of data access, and unlimited users.
- Pro costs $199 a month with 100,000 units and 3 years of data access, and Enterprise costs $2,499 a month.
- Extra units cost $8 per 100,000.
- A unit is one trace, one observation, or one score.
- The MIT-licensed core is free to self-host with no usage cap, though a production install needs PostgreSQL, ClickHouse, Redis, and S3-compatible stora
Pros
- Hobby tier is free with 50,000 units a month
- Core is a flat $29 a month with no per-seat charge
- MIT core is free to self-host
Cons
- One agent run can consume dozens of units, so volume grows fast
- Pro costs $199 a month for the same 100,000 units as Core
LangSmith
Best for: Teams building on LangChain or LangGraph
LangSmith is LangChain’s managed platform for tracing, evaluation, prompt management, and agent monitoring. The Developer plan is free for one seat with 5,000 base traces a month and 14-day retention. Plus costs $39 per seat per month with 10,000 base traces a month shared by the whole organization and one free small serverless deployment.
- Enterprise is custom priced and is the only tier that permits self-hosting or a hybrid deployment.
- Usage past the included allowance is billed in LangChain Standard Units, where one unit costs $1.
- The platform adds datasets, experiments, annotation queues, a prompt hub, and a playground.
- One limit to plan around is that the 10,000 included traces on Plus do not grow with seats, so a 10-person team starts at $390 a month in seat charges
Pros
- Deep integration with LangChain and LangGraph tracing
- annotation queues, prompt hub, and playground included
- one free small serverless deployment on Plus
Cons
- Developer plan is limited to one seat
- seat charges stack on top of usage charges
Arize Phoenix
Best for: OpenTelemetry teams comparing RAG and agent runs
Arize Phoenix is the open, local-first half of the Arize stack, built on OpenTelemetry and the OpenInference conventions. Phoenix handles tracing, evaluation, prompt management, and experimentation, and it runs locally or in a container. The hosted product, Arize AX, has a Free tier with 25,000 spans a month, 1 GB of ingestion, 15-day retention, and unlimited users.
- AX Pro costs $50 a month for 50,000 spans, 10 GB of ingestion, and 30-day retention.
- Enterprise is custom priced and adds self-hosted deployment, single sign-on, audit logs, and the Alyx debugging assistant.
- Phoenix fits teams that already instrument with OpenTelemetry, because the same instrumentation carries over to AX.
- Evaluations include LLM-as-a-judge checks, code evaluators, and integrations with Ragas and DeepEval.
Pros
- Phoenix is free to self-host with no usage caps
- every AX tier includes unlimited users, evals, and experiments
- OpenTelemetry native tracing
Cons
- No overage rate is published past the span allowance
- Phoenix uses the Elastic License 2.0, which bars offering it as a hosted service to others
W&B Weave
Best for: ML teams already using Weights and Biases
W&B Weave is the LLM evaluation and observability product from Weights and Biases, now part of CoreWeave Forge after the acquisition completed on 5 May 2025. The Free plan costs $0 with 5 GB of storage, 1 GB of Weave ingestion a month, and up to 5 model seats. Pro starts at $60 a month with 100 GB of storage, 1.5 GB of Weave ingestion, and up to 10 model seats.
- Extra ingestion on Pro costs $0.10 per MB, and Enterprise is custom priced with extra ingestion at $0.20 per MB.
- Weave traces agents through Python and TypeScript SDKs and runs evaluations with LLM-as-judge scorers and custom scorers.
- In September 2026 CoreWeave put Agent Lens into public preview as the successor to Weave for agent tracing.
- Choose Weave when your team already lives in Weights and Biases.
Pros
- Evals sit beside training runs in one account
- free academic plan includes 25 GB of ingestion a month
- SDK is Apache 2.0
Cons
- Extra ingestion on Pro costs $0.10 per MB, the steepest meter in this list
- Weave has no standalone plan, so LLM-only teams buy the whole platform
Helicone
Best for: Self-hosted request logging and cost tracking
Helicone is an open-source AI gateway and observability platform that logs requests and tracks cost and latency. The Hobby plan is free with 10,000 requests a month, 1 GB of storage, one seat, and 7-day retention. Pro costs $79 a month with unlimited seats, 1-month retention, alerts, and reports, plus usage-based charges past the included 10,000 requests.
- Team costs $799 a month with 5 organizations and 3-month retention.
- The important fact about Helicone is its status: Mintlify acquired Helicone on 3 March 2026 and put the hosted product into maintenance mode, and the
- The Apache 2.0 self-hosted version stays open to everyone with no request cap.
- Choose Helicone to self-host a gateway and log every request without a markup on token cost.
Pros
- Self-hosted version is Apache 2.0 with no request cap
- no markup on model token cost
- free Hobby tier needs no card
Cons
- Hosted product is in maintenance mode and new signups are disabled
- Pro adds usage-based charges on top of the $79 monthly fee
Braintrust
Best for: Teams tracking eval quality across releases
Braintrust is an evaluation-first platform for LLM applications, with datasets, experiments, scorers, a playground, and production tracing in one workspace. The Starter plan is free with $10 a month in model credits, 1 GB of processed data, 10,000 scores, and 14-day retention. Pro costs $249 a month with $100 a month in model credits, 5 GB of processed data, and 50,000 scores.
- Extra processed data on Pro costs $3 per GB and extra scores cost $1.50 per 1,000.
- Enterprise is custom priced and adds custom role controls, SAML single sign-on, a business associate agreement, and self-hosted deployment.
- Every experiment run is recorded, scored, and compared with earlier runs in a diff view, which sets Braintrust apart for teams that ship model changes
- Human review scorers, custom charts, and sandbox evals sit on Pro, and retention can extend to 180 days at $0.50 per GB a month.
Pros
- Unlimited users, projects, datasets, and experiments on every tier
- experiment history with diff views across runs
- Pro includes $100 a month in model credits
Cons
- No tier exists between free Starter and $249 Pro
- custom role controls and single sign-on need the Enterprise plan
How we chose
We picked platforms that run the same prompts or datasets against more than one model and show the results side by side, with a dataset, experiment, or scoring view. Prices and plan limits come from official vendor pricing pages and docs opened on 12 November 2026, and every figure here is tied to a Source link below. We did not test any tool hands-on. We ranked nothing by customer counts, awards, or review scores.
Pick by monthly volume and team size
| Situation | Pick | Why the numbers fit |
|---|---|---|
| Solo developer, code-first tests | Promptfoo | $0 forever, 10,000 red-team probes a month |
| Small team, hosted, under 50,000 units | Langfuse Hobby | $0, 50,000 units a month, 2 users |
| Small team, hosted, under 25,000 spans | Comet Opik Free Cloud | $0, 25,000 spans a month, 10 members |
| Team under 100,000 spans, cheapest hosted entry | Comet Opik Pro | $19 a month, 100,000 spans, then $5 per 100,000 |
| LangChain team of 5 | LangSmith Plus | $195 a month in seats, 10,000 traces included |
| Team that outgrows free spans | Arize AX Pro | $50 a month, 50,000 spans, unlimited users |
| ML team already on W&B | W&B Weave Pro | $60 a month, 1.5 GB ingestion, then $0.10 per MB |
| Team tracking quality across releases | Braintrust Pro | $249 a month, 50,000 scores, 5 GB processed data |
Frequently asked questions
What is the cheapest way to compare AI model results?
Promptfoo costs $0 forever for its Community edition, which runs the same prompts across many providers from a YAML file and includes red teaming up to 10,000 probes a month. Opik Free Cloud costs $0 for 25,000 spans a month and Langfuse Hobby costs $0 for 50,000 units a month.
Which platform is best for comparing models in CI?
Promptfoo is the best fit for CI because tests live as YAML files in version control and run from the command line on every change. Langfuse, Opik, and Braintrust also run dataset experiments, but they are hosted workspaces rather than a test runner for a build step.
Which platform is best for a small team on a tight budget?
Langfuse Hobby is the best budget pick for most small teams: free up to 50,000 units a month with 2 users, then a flat $29 a month with no per-seat charge. Opik Free Cloud is the best alternative for span-based workloads, with 25,000 spans a month free and Pro at $19 a month.
How much does it cost to run evals at production volume?
It depends on the meter. Opik Pro at $19 a month covers 100,000 spans, Langfuse Core at $29 a month covers 100,000 units, and Braintrust Pro at $249 a month covers 50,000 scores. Overages add $5 per extra 100,000 spans on Opik, $8 per extra 100,000 units on Langfuse, and $1.50 per extra 1,000 scores on Braintrust.
Can I compare models without a subscription plan?
Yes. All eight platforms in this article have a free tier that lets you run real comparisons. The most restrictive is LangSmith Developer at one seat and 5,000 traces a month, while Langfuse Hobby allows 50,000 units a month and Opik Free Cloud allows 25,000 spans a month.
What happened to Helicone?
Mintlify acquired Helicone on 3 March 2026 and put the hosted product into maintenance mode, with feature development stopped. The hosted sign-in page states that new signups are disabled, so new users should use the Apache 2.0 self-hosted version, which has no request cap.
Sources
- https://www.promptfoo.dev/
- https://www.promptfoo.dev/pricing
- https://www.comet.com/
- https://www.comet.com/site/pricing/
- https://langfuse.com/
- https://langfuse.com/pricing
- https://www.langchain.com/langsmith
- https://www.langchain.com/pricing
- https://arize.com/
- https://arize.com/pricing/
- https://wandb.ai/
- https://www.helicone.ai/
- https://www.helicone.ai/pricing
- https://www.braintrust.dev/
- https://www.braintrust.dev/pricing
Prices and features were read on each company’s own website in November 2026. They change often, so confirm the current offer on the official site before you sign up or buy.