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Open Source IT Infrastructure Monitoring Tool

Get More with Nagios CSP

Before downloading Nagios Core alone, consider the Nagios Core Services Platform — a free, unified bundle that includes Core plus a pre-built VM running a free edition of Nagios XI, our flagship monitoring solution with smart wizards, advanced reporting, and insightful dashboards. See what’s included.

Nagios XI (free VM) Nagios Core Official Plugins NCPA NRPE NSClient++ NagVis 12+ Community Plugins

Just download Core

Years in Production

Community Add-ons

Downloads per Year

Users Worldwide

What is Nagios Core?

Trusted by 1M+ users worldwide, Nagios Core provides complete monitoring of your entire IT infrastructure environment – including websites, DNS, servers, routers, switches, services, servers, workstations, and more.

Servers – (Linux, Windows, Unix) – Monitor CPU, memory, disk, processes
Network Devices – Switches, routers, firewalls, load balancers
Websites & Applications – Uptime, response time, content verification
Services– DNS, DHCP, FTP, SSH, email, databases
Custom Metrics – Extensible with thousands of plugins

Why Choose Nagios Core?

Proven Reliablity

Downloaded millions of times since 2002, Nagios Core is the industry standard for open source IT monitoring.

100% Free

No licensing costs, no hidden fees, no limitations. Completely free forever under GPL v2 license.

Highly Extensible

Works with thousands of community-developed plugins and integrations. Customize monitoring for any environment.

Enterprise-Grade

Trusted by Fortune 500 companies, government agencies, and organizations worldwide for mission-critical monitoring.

Nagios Core Source Code

For developers and advanced users who need complete control:

✓ Full source code access for customization

✓ Install on any Linux distribution

✓ Build custom monitoring solutions

✓ Contribute to open source development

Download Nagios Core Source

https://github.com/NagiosEnterprises/nagioscore.git

The #1 Open Source Monitoring Solution For IT

Nagios Core has been downloaded millions of times for good reason – it’s the industry standard in open source monitoring for all environments, large and small.

Websites & Web Applications

Monitor uptime, response time, SSL certificates, content changes

Servers & Workstations

Track CPU, memory, disk usage, running processes, system health

Network Infrastructure

Monitor switches, routers, firewalls, ports, bandwidth, traffic

Applications & Services

Database servers, email systems, DNS, DHCP, custom applications

Cloud Infrastructure

AWS, Azure, Google Cloud, and other cloud platforms

Custom Metrics

Anything you can measure with a script or plugin

View Full Features

System Requirements

Minimum requirements for Nagios Core

Hardware Requirements

CPU: 2 cores minimum (4+ recommended for larger deployments)
RAM: 2GB minimum (4GB+ recommended)
Disk: 20GB free space minimum
Network: Reliable network connectivity

Supported Linux Distributions

Ubuntu 20.04 LTS, 22.04 LTS, 24.04 LTS
CentOS 7, 8, Stream
Debian 10, 11, 12
Red Hat Enterprise Linux 7, 8, 9
Other Linux distributions (may require manual configuration)

Software Requirements

Web Server: Apache 2.x or Nginx
PHP: Version 7.0 or higher
C Compiler: GCC or compatible for building from source

Operating System

Linux-based OS (Ubuntu, CentOS, Debian, RHEL, or compatible)

View Detailed Installation Requirements

Nagios Core vs Nagios XI - Which is Right for You?

Feature	Nagios Core (Free)	Nagios XI (Commercial)
Cost	100% Free	Paid
License	Open Source (GPL v2)	Commercial
Configuration	Text-based config files	Web-based GUI
Setup	Manual installation	Automated wizards
Dashboards	Basic web interface	Advanced dashboards
Reports	Basic reports	Professional reports
Configuration Wizards	Not Included	Included
Support	Community forums	Professional support
Updates	Manual	Automatic
Backup/Restore	Manual	Automated
Best For	IT pros comfortable with CLI	Teams needing quick deployment

Bottom Line: Nagios Core is perfect for technical teams who want complete control and no licensing costs. Nagios XI is ideal for organizations that need a polished web interface and professional support.

Learn More About Nagios XI

Resources & Support

Documentation

Developer Resources

Community & Support

Ready to Start Monitoring?

Join thousands of organizations who trust Nagios for their infrastructure monitoring.

Open Source IT Infrastructure Monitoring Tool​