kitio.aiOpik vs Fiddler AI
A side-by-side look at pricing plans, free tiers, features, pros and cons, updated for 2026. Opik starts at $19/mo and Fiddler AI starts at See pricing page. Check both pricing pages for current plans.
At a glance
Best for
Category
Pricing model
Starting price
Free plan
Made by
Based in
Rating
Key features
- Tracing and spans
- Evaluation metrics
- Agent optimizer
- Guardrails
- Framework integrations
- Agent tracing and observability
- Continuous evaluations
- Real-time guardrails
- ML model monitoring
- AI governance and compliance
- Custom evaluators
| Feature | Opik | Fiddler AI |
|---|---|---|
| Best for | Comet's open-source platform for LLM tracing and evaluation | Evaluation, observability and guardrails for AI agents and ML models |
| Category | Models & APIs | Models & APIs |
| Pricing model | Freemium | Freemium |
| Starting price | $19/mo | See pricing page |
| Free plan | Yes | Yes |
| Made by | Comet | Fiddler Labs |
| Based in | United States | United States |
| Rating | No ratings yet | No ratings yet |
| Key features |
|
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Pricing compared
Opik starts at $19/mo and Fiddler AI starts at See pricing page. Check both pricing pages for current plans.
Free plan
Cheapest paid plan
Top plan
Free trial
4 plans
Open Source
Free
- Self-hosted
- Full observability feature set
- Unlimited spans
Free Cloud
Free
- Up to 10 team members
- 25k spans per month
- 60-day data retention
Pro Cloud
$19/mo
- Up to 50 team members
- 100k spans per month
- $5 per extra 100k spans
Enterprise
Custom
- Unlimited team members
- Flexible deployments
- Single sign-on
- 2-hour response SLA
2 plans
Developer
$0.002 / trace
- Custom evaluators
- Bring your own judge
- RBAC and SSO
- SaaS deployment
Enterprise
Contact sales
- Enterprise guardrails
- SaaS, VPC or on-prem
- Named success manager
Prices in USD, checked Oct 28, 2026 or later. Plans change often, so confirm on each tool's site before you buy.
Pros and cons
Opik
- Free and self-hostable
- Automatic prompt optimization
- Many integrations
- Smaller community than Langfuse
- Hosted plan limits vary
- Docs split with Comet ML
Fiddler AI
- Covers both LLM agents and classic ML
- Pay-per-trace developer pricing
- Self-hosted and VPC options
- Enterprise features need a sales contract
- Free tier limits are not spelled out
- Broad platform with a learning curve
Which one should you choose?
Choose Opik if you want:
- Free and self-hostable
- Automatic prompt optimization
- Many integrations
Watch out: smaller community than langfuse.
Choose Fiddler AI if you want:
- Covers both LLM agents and classic ML
- Pay-per-trace developer pricing
- Self-hosted and VPC options
Watch out: enterprise features need a sales contract.
Opik vs Fiddler AI FAQ
What is the difference between Opik and Fiddler AI?
Opik: Comet's open-source platform for LLM tracing and evaluation. Fiddler AI: Evaluation, observability and guardrails for AI agents and ML models. Both are models & apis tools.
Is Opik or Fiddler AI cheaper?
Opik starts at $19/mo and Fiddler AI starts at See pricing page. Check both pricing pages for current plans.
Do Opik and Fiddler AI have free plans?
Opik: Yes. Fiddler AI: Yes.
Who makes Opik?
Opik is made by Comet, based in United States.
Who makes Fiddler AI?
Fiddler AI is made by Fiddler Labs, based in United States.
Which should I choose, Opik or Fiddler AI?
Choose Opik if you value free and self-hostable and automatic prompt optimization. Choose Fiddler AI if you value covers both llm agents and classic ml and pay-per-trace developer pricing.