Nagios Core
Nagios Core: A free, extensible monitoring engine for teams comfortable with self-hosted configuration. Ranked #8 of 38 in Server Monitoring by our editors (8.7/10); pricing: Free plan; best for free extensible monitoring with a large ecosystem.
At a glance
- Editor score8.7 / 10
- PricingFree plan
- Best forFree extensible monitoring with a large ecosystem
- Free planYes
- Paid fromFree
- Facts checked20 Sep 2026
Where it wins
- Free, GPL-licensed, self-hosted monitoring engine
- Plugin architecture supports custom checks and metrics
- Integrates with Grafana, Prometheus, Slack, and ServiceNow
Where it doesn't
- Configuration relies mainly on text files and command-line workflows
- The platform listing is limited to Linux
- It lacks a server auto-discovery feature
Our verdict on Nagios Core
Nagios Core is a free, GPL-licensed, self-hosted monitoring engine for IT infrastructure. It monitors servers, workstations, network devices, websites, applications, services, and custom metrics through a plugin-based architecture. Its scope suits teams that want broad infrastructure coverage and control over monitoring logic, particularly when custom checks, agents, or remote execution methods are part of the operating model.
The monitoring surface is broad. Nagios Core covers CPU, memory, disk usage, processes, system health, network protocols, services, devices, bandwidth, availability, websites, applications, databases, mail, and directory services. Alerting includes email, pager, SMS, user-defined notifications, escalation paths, time-based alerting, dependencies, and flap detection. Event handlers can support automated remediation and service recovery. The CGI web interface provides notification and problem history, availability reports, and performance-data export. Integrations with Grafana, InfluxDB, Prometheus, PagerDuty, Slack, and ServiceNow extend its reporting and incident workflows.
Its main trade-off is operational convenience. Configuration is primarily managed through text files and command-line workflows, and the plugin-oriented model places responsibility on the team to define checks and maintain its monitoring setup. Nagios Core also presents a Linux-only platform listing, while its monitoring model supports Linux, Unix, and Windows targets through native checks, agents, and remote execution methods. Choose it for free, extensible monitoring with a large ecosystem and detailed control over checks, alerts, and remediation. Teams seeking a more guided setup or less manual configuration should consider an alternative.
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Nagios Core pricing
Nagios Core fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| Included hosts | Not verified |
| Metric retention | Not verified |
| Monitoring method | Hybrid |
| Supported operating systems | Linux, Unix, Windows |
| Server auto-discovery | Not verified |
| Process monitoring | Yes |
| Container monitoring | Not verified |
| Deployment | Self-hosted |
| Platforms | Linux |
| Support | Community, Docs |
| Built for | Small business, Mid-market, Enterprise (editorial estimate) |
| Integrations | 6 integrations: Grafana, InfluxDB, Prometheus, PagerDuty, Slack, ServiceNow |
| Pricing | Free plan |
| Website | nagios.org |
| Facts checked | 20 Sep 2026 |
Nagios Core integrations
Nagios Core lists 6 integrations on its own site.
- Grafana
- InfluxDB
- Prometheus
- PagerDuty
- Slack
- ServiceNow
Alternatives to Nagios Core
- CheckmkA broad monitoring platform with a free edition and high paid entry price.9.4
- ZabbixA broad monitoring platform with a free self-hosted edition and managed cloud options.9.3
- NetdataAffordable infrastructure visibility with per-second metrics, logs, alerts, and AI assistance.9.2
See all Nagios Core alternatives →
Nagios Core vs the competition
- Nagios Core vs Checkmk
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- Nagios Core vs Paessler PRTG Network Monitor
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Also Ranked In
Nagios Core is ranked in 2 of our directories.
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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