Skip to content
Network List

Nagios (Core / XI)

The classic host and service monitor — free Core, commercial XI.

Freemium Desktop download

Reviewed by Paul Jens Handschuh, Network administrator Updated 2026-11-05

Official site www.nagios.org
Platforms
Linux/Unix server, web UI
Licence
Freemium — Core GPLv2 / XI commercial
Price
Core free; XI from ~$2,595 (100 nodes)
Category
Monitoring & observability
Updated
2026-11-05

What it is

Nagios is a long-running monitoring system: a free Core engine and a commercial XI edition with an extended web UI. It checks host, service and resource availability and notifies on failures, and a vast plugin ecosystem widens what it can watch.

Problems it removes

  • You want a proven, scriptable availability monitor with a huge plugin library.
  • A simple up/down and threshold model suits the team better than full observability.

How administrators use it

  • Define hosts and services in config and reuse community plugins for checks.
  • Wire notifications to email or chat with escalation.
Nagios Core current network status view
Screenshot: Wikimedia Commons, CC BY-SA 4.0.

Strengths & trade-offs

Strengths

  • Battle-tested and scriptable.
  • Enormous plugin ecosystem.
  • Free Core edition.

Trade-offs

  • Config is text-file heavy.
  • Core has a dated UI; polish lives in paid XI.

Common questions

What is the difference between Nagios Core and XI?

Core is the free, config-driven engine; XI is the commercial edition with a richer web UI, configuration tools and support.

Is Nagios still worth using?

Yes for straightforward availability monitoring with a huge plugin library, though newer tools offer slicker interfaces.

Zabbix Linux/Unix server, web UI; agents for Windows/Linux/macOS/Unix

Open-source monitoring for servers, network gear, VMs and applications.

desktop download Prometheus Linux/Windows/macOS, web UI; CNCF

Time-series monitoring and alerting, the default for cloud-native systems.

desktop download PRTG Network Monitor Windows server + web/mobile; also SaaS (Hosted Monitor)

Sensor-based network and infrastructure monitoring from Paessler.

cloud + desktop