What is Nagios Core used for?

Nagios Core is a long-running host, service and network monitoring program written in C, with plugins, alerting and an optional web interface. It is a good fit for watching servers and services in a small data center, and alerting on-call staff when a service fails.

Is Nagios Core open source?

Yes. Nagios Core is open source under the GPL-2.0 licence. Its source code is on GitHub at NagiosEnterprises/nagioscore and is written mainly in C.

Yes. Nagios Core is open source, so the software itself is free to use.

Can I self-host Nagios Core?

Yes. Nagios Core can be self-hosted on your own server or infrastructure; there is no official hosted version.

What is Nagios Core an alternative to?

Nagios Core is an open-source alternative to Datadog, PRTG Network Monitor, SolarWinds Observability and LogicMonitor. Other open-source alternatives to Datadog include Zabbix, Checkmk and Netdata.

Is Nagios Core actively maintained?

Yes. The most recent commit to Nagios Core was on 7 August 2026. The project has 2k stars on GitHub.

Nagios Core: open-source alternative to Datadog

About Nagios Core

Nagios Core is a monitoring program for hosts, services and networks, written in C and released under the GNU General Public License version 2. It checks whether your systems and services are working and tells you when something goes wrong or recovers.

It can monitor network services such as SMTP, POP3, HTTP and ping, as well as host resources like processor load and disk usage. A plugin interface lets you write your own checks. You can define a host hierarchy with parent hosts, which lets Nagios tell hosts that are down apart from hosts that are only unreachable. Notifications go out by email, pager or a user-defined method, and event handlers allow automatic responses to problems.

Other features include automatic log file rotation and archiving, plus CGI programs that provide an optional web interface for current status, notification history and logs. Documentation, quickstart installation guides, a user guide and support forums are available from the Nagios site. Paid Nagios products exist separately from this open-source core.

Key features

Monitors network services such as HTTP and SMTP
Tracks host resources like CPU load and disk
Plugin interface for custom checks
Parent host hierarchy to separate down from unreachable
Email, pager and custom notifications
Event handlers for automated responses
Optional web interface for status and history

Good fit for

→Watching servers and services in a small data center
→Alerting on-call staff when a service fails

Built with: C
Tags: monitoring; nagios; network-monitoring; alerting; plugins; c-language; self-hosted

Nagios Core: questions and answers

What is Nagios Core used for?: Nagios Core is a long-running host, service and network monitoring program written in C, with plugins, alerting and an optional web interface. It is a good fit for watching servers and services in a small data center, and alerting on-call staff when a service fails.
Is Nagios Core open source?: Yes. Nagios Core is open source under the GPL-2.0 licence. Its source code is on GitHub at NagiosEnterprises/nagioscore and is written mainly in C.
Is Nagios Core free?: Yes. Nagios Core is open source, so the software itself is free to use.
Can I self-host Nagios Core?: Yes. Nagios Core can be self-hosted on your own server or infrastructure; there is no official hosted version.
What is Nagios Core an alternative to?: Nagios Core is an open-source alternative to Datadog, PRTG Network Monitor, SolarWinds Observability and LogicMonitor. Other open-source alternatives to Datadog include Zabbix, Checkmk and Netdata.
Is Nagios Core actively maintained?: Yes. The most recent commit to Nagios Core was on 7 August 2026. The project has 2k stars on GitHub.