A client rings to say the shared drive's gone, and you're the last to find out. Free network monitoring stops that, and nearly every free option is open source and self-hosted, so you trade setup time for a licence. Choose by approach, from auto-discovery and metrics to classic checks and plain uptime, then check which edition each feature sits in.
This page is for IT admins, MSP owners and small-business operators who want servers and networks watched without buying a licence. Every tool here says on its own website that it's open source or has a free edition. Products whose pages only offer a free trial are left out. The nine are named, not linked, and they're in no particular order.
Get a first alert working in five moves
- Write down what has to be watched: switches, servers, key applications and the websites customers use.
- Decide where the monitor will live, on a machine or virtual server you'll keep running and patched, because a self-hosted tool is only as reliable as the box it sits on.
- Pick one approach from the groups further down and install a single tool, not three.
- Add a handful of devices first, then send a test alert to a phone or inbox someone reads out of hours.
- Break something on purpose, such as stopping a test service, and time how long the alert takes to reach you.
Once that works, add the rest of your estate a section at a time, and write down how to restore the monitor itself if its own server fails. That's the step people skip. A monitor that goes down quietly is worse than none, because you'll trust the silence.
What free means on these pages
Nearly every free option here is open source and self-hosted. You don't pay for a licence, but you pay with time: installing it, keeping it patched, backing up its settings and upgrading it when a new version lands. For a one-person IT desk that's a real demand on your hours, and it's worth being honest about before you start.
Plan those hours before you install anything. Put a recurring slot in the diary for updates, decide who covers when you're away, and keep a written note of every device and check you add. Free software with nobody looking after it ends up as one more thing on the network that needs watching, and that's the opposite of what you wanted when you started.
It also explains what's missing. Commercial monitoring products appear on the same kind of search results, but where a vendor's page only states a free trial, PRTG being one example, it isn't on this list. A trial is a way to evaluate something you'll later buy, and that's a different decision from running a free tool for years.
Community, core and commercial editions
When you read a feature list, check which edition it belongs to. It's easy to fall for a feature in a product tour and then find it lives in the commercial edition, not the one you installed. Ask in the community forum or read the edition comparison on the vendor's own site before you plan around anything.
Three of the nine split their offer between a free edition and a commercial one. Checkmk describes its Community edition as free and open-source monitoring for small infrastructures. Nagios describes its core edition as free monitoring and alerting for servers, networks and applications. OpenNMS is published under the AGPLv3 licence, with a commercial subscription called Meridian sitting beside it.
Four ways these tools watch a network
Auto-discovery
LibreNMS is an autodiscovering network monitoring system built on PHP and MySQL, which means it finds devices rather than waiting for you to list them. The Community edition mentioned above also discovers and monitors cloud and on-premises systems, and the AGPLv3 platform is built for distributed infrastructure across several locations.
Metrics and alerting
Prometheus stores metrics in a time series database and alerts on them, and the project describes itself as the leading open-source monitoring solution. Netdata focuses on real-time monitoring with per-second metrics, so it's the one to look at when you want to see what's happening right now.
Classic checks
Icinga is built around custom checks and alerts for networks and servers. Zabbix calls itself an enterprise-class, open-source monitoring solution for network and application monitoring. The core edition described earlier belongs in this group too.
Plain uptime checks
Uptime Kuma is a self-hosted tool for uptime checks, and it's the simplest thing here if all you need to know is whether something's responding. If that's the whole job, my guide to free uptime monitoring goes further on that single task.
The nine at a glance
| Tool | Approach | Who it suits |
|---|---|---|
| Checkmk | Auto-discovery monitoring | Small infrastructures across cloud and on-premises |
| Icinga | Check-based monitoring | Admins writing custom checks for networks and servers |
| LibreNMS | Auto-discovery network monitoring | Networks you'd rather discover than list by hand |
| Nagios | Classic check-based monitoring | Servers, networks and applications watched with alerts |
| Netdata | Real-time observability agent | Live, per-second views of infrastructure |
| OpenNMS | Enterprise network monitoring | Distributed infrastructure |
| Prometheus | Metrics and alerting | Teams storing time series metrics and alerting on them |
| Uptime Kuma | Self-hosted uptime monitor | Checking that sites and services stay up |
| Zabbix | Enterprise open-source monitoring | Network and application monitoring in one tool |
Nine free options, A to Z
Checkmk
Best for: Small infrastructures that want cloud and on-premises systems discovered and watched, using the free, open-source Community edition rather than a commercial one.
Icinga
Best for: Admins who like writing their own checks and alerts for networks and servers; the project's pitch is infrastructure monitoring you own.
LibreNMS
Best for: Network teams who'd rather the system found devices for them; it's an autodiscovering network monitoring system built on PHP and MySQL.
Nagios
Best for: Watching servers, networks and applications with alerting from the self-hosted core edition, which the project describes as free.
Netdata
Best for: Seeing what's happening across your infrastructure right now, with metrics collected every second.
Want AI doing the heavy lifting in your marketing?
I build the systems that handle the boring 80 percent, so you get your week back. Done properly, with the human kept in.
OpenNMS
Best for: Organisations with distributed infrastructure that want an AGPLv3 platform, with a commercial Meridian subscription available beside it.
Prometheus
Best for: Engineers who want metrics in a time series database with alerting on top; the project calls itself the leading open-source monitoring solution.
Uptime Kuma
Best for: Small teams that only need to know when a site or service stops responding, from a tool they host themselves.
Zabbix
Best for: Businesses wanting network and application monitoring from an open-source tool its makers describe as enterprise-class.
For an MSP or a one-person IT desk
Pick the approach that matches the problem you've got today, not the one you might have in three years. If clients ring you before your monitor does, start with uptime and a few classic checks on the things they use. For a plain ping and a public status page, uptime and status page tools may fit better. If you're managing a network you didn't build, start with auto-discovery so you can see what's there. Keep the setup notes somewhere other than the monitoring server, and test the alerts every time you change something.
If you'd rather hand the hosting and upkeep to a vendor, my list of the best network monitoring software includes commercial options alongside these.
Do you make network or infrastructure monitoring software? Tool makers can ask to be considered for a featured place on this list.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
Can a business use these network monitoring tools for free?
Each one describes itself on its own website as open source or as having a free edition. Read the licence and edition details on the project's page for the version you install.
What's the difference between a free edition and a commercial one?
Some vendors here offer a free community or core edition beside a commercial edition or subscription. Features can sit in one and not the other, so check before you plan around one.
Do I need my own server to run free network monitoring?
Usually, yes. Almost every option here is self-hosted, so you'll need a machine or virtual server to run it and someone to keep it patched.
Can free tools find devices on my network automatically?
Several describe auto-discovery, finding devices and systems for you rather than waiting for you to list them. Others expect you to define what to check.
Do free editions and their limits change?
Yes. What each edition includes can change between versions, so check the vendor's page before you build your monitoring around a particular feature.
Is uptime monitoring the same as network monitoring?
Not quite. Uptime monitoring checks whether a site or service responds, while network monitoring watches devices, servers and applications in more depth. Many small teams start with uptime and add more later.
