Nagios vs Prometheus: Pricing and Ratings Compared (2026)
Entry prices and free plans as read on each vendor's pricing page, and user ratings as published on review sites, for Nagios and Prometheus side by side. This page compares data; it is not a hands-on review.
On the data: On the data below the two are close or not directly comparable, so we do not name a winner for this pair.
Short on time? Here's the quick answer
Based on published vendor pricing and features and on public review data, here's who should pick what:
Nagios
The industry standard in open-source IT monitoring tools for servers, networks, applications, and services.
Best for you if:
- • You want legacy monitoring standard
Prometheus
Monitoring and alerting toolkit
Best for you if:
- • You want a fully free tool (Nagios requires payment)
| At a Glance | Nagios | Prometheus |
|---|---|---|
Starts at | Free plan | Free 100% free |
Category | Monitoring Cloud & Infrastructure | DevOps Monitoring |
Rating | 4.5/5 G2 4.5 58 reviews | 4.5/5 G2 4.5 61 reviews |
Free plan | Yes | Yes |
Watch out for | n/a | Storage costs grow linearly with metric cardinality and retention period |
Choose Nagios or Prometheus?
Choose Nagios if
- You want legacy monitoring standard
- You want highly customizable
- You work in monitoring, not DevOps
Choose Prometheus if
- You want a fully free tool (Nagios requires payment)
- You want industry standard
- You want great for metrics
- You work in DevOps, not monitoring
In-Depth Analysis
Nagios
The industry standard in open-source IT monitoring tools for servers, networks, applications, and services.
Nagios' pricing model, with a robust free tier and one-time purchase options for commercial versions, is quite generous compared to many subscription-based monitoring tools.
Strengths
- Pro: Legacy monitoring standard
- Pro: Highly customizable
- Pro: Large plugin library
- Pro: Free and open source
- Pro: Battle-tested
Weaknesses
- Con: UI very dated
- Con: Configuration complex
- Con: Scaling difficult
- Con: Setup time-consuming
- Con: Alternatives more modern
Key features
Prometheus
Monitoring and alerting toolkit
Prometheus is 100% free and open source (Apache 2.0).
Watch out
Storage costs grow linearly with metric cardinality and retention period
Strengths
- Pro: Industry standard
- Pro: Great for metrics
- Pro: Open source
Weaknesses
- Con: Long-term storage
- Con: Learning curve
Key features
Plans and prices: Nagios vs Prometheus
| Tool | Plans and prices | Source |
|---|---|---|
| Nagios |
| nagios.org read Sep 30, 2026 |
| Prometheus |
| prometheus.io read Oct 2, 2026 |
Prices as read on each vendor's own pricing page on the date shown. Plans are listed per tool and are not matched against the other tool's plans: a plan name or price in one column says nothing about the same row in the other. Details on Nagios pricing and Prometheus pricing.
Key Takeaways
Nagios
- Choose if you want the industry standard in open-source IT monitoring tools for servers, networks, applications, and services
Prometheus
- Choose if you want monitoring and alerting toolkit
What the data shows
On the data below the two are close or not directly comparable, so we do not name a winner for this pair.
- User ratings are within 0.2 points (4.5/5 from 58 reviews for Nagios, 4.5/5 from 61 reviews for Prometheus).
- Both have a free plan.
Criteria: user rating (only above 20 reviews on both sides, gap of 0.2 or more), entry price (only on the same billing basis), free plan. How we rate
Frequently Asked Questions
How do Nagios and Prometheus compare in 2026?
On the data below the two are close or not directly comparable, so we do not name a winner for this pair. User ratings are within 0.2 points (4.5/5 from 58 reviews for Nagios, 4.5/5 from 61 reviews for Prometheus). Both have a free plan.
What are Nagios and Prometheus used for?
Nagios: The industry standard in open-source IT monitoring tools for servers, networks, applications, and services. Prometheus: Monitoring and alerting toolkit.
What does Nagios cost vs Prometheus?
Nagios has no public paid-plan price on file. Prometheus is free. Prices read on the vendors' pricing pages, latest check Oct 2, 2026.
What's the main difference between Nagios and Prometheus?
Nagios's main strength: legacy monitoring standard. Prometheus's main strength: industry standard.