Checkmk Community vs PRTG Freeware: Which Free Monitor Fits

If you need free infrastructure monitoring and the choice has come down to Checkmk Community or PRTG Freeware, the short answer is this: pick PRTG Freeware when your monitoring server will be a Windows machine and you only need to watch about ten devices. Pick Checkmk Community when you can run a Linux server or a container, have more than a handful of hosts, or want no hard cap on what you monitor. Both are free to use, but they are free in different ways, and the difference decides which one fits.

The short comparison

How each one counts what you monitor

This is the part that surprises people. PRTG counts sensors, not devices. One sensor is one measurement: a ping, a switch port, a disk, a service. Paessler’s own FAQ says you need on average about 5 to 10 sensors per device, or one sensor per switch port. A 100-sensor allowance is therefore a budget, and a single 48-port switch monitored port by port could eat half of it.

Checkmk Community does not enforce a limit like this. The vendor’s editions page describes Community as scalable up to roughly 100 hosts, which is sizing guidance rather than a licence block. Checkmk discovers the services on each host (file systems, interfaces, processes) and proposes checks for them, so you are limited by server capacity and your own patience, not by a counter.

Platforms and what you have to run

PRTG’s core server runs on Windows Server 2016 to 2025 and on Windows 10 and 11, with .NET Framework 4.7.2 or later (4.8 is recommended for new installs). For up to 500 sensors Paessler recommends 4 CPU cores, 4 GB of RAM and 100 GB of disk, which is generous for the 100 sensors the free edition allows. Linux machines can host probes (Ubuntu, Debian, RHEL, Raspberry Pi OS) that report to the Windows core, but the core itself does not run on Linux.

Checkmk’s server side is the reverse: Linux only. The download page offers packages for Ubuntu, Debian, SLES and Red Hat, a Docker image and a virtual appliance. Windows, Linux, Unix and macOS machines are monitored through the Checkmk agent, which listens on TCP 6556 by default.

Getting started with Checkmk Community

The quickest test is Docker:

docker container run -dit 
  --name monitoring 
  -e CMK_PASSWORD='ChangeThisPassword' 
  -p 8080:5000 -p 8000:8000 
  -v monitoring:/omd/sites 
  --restart always 
  checkmk/check-mk-community:2.5.0-latest

Open http://<docker-host>:8080/cmk/check_mk/ and sign in as cmkadmin with that password. For a package install on Linux, the official setup guide creates a site as root and starts it as the site user:

omd create --admin-password 'ChangeThisPassword' mysite
su - mysite
omd start
omd status

The site then answers at http://<server>/mysite. Add hosts under Setup, run service discovery on each, accept the services found and activate the pending changes. For production, put the web interface behind HTTPS.

One naming note: Checkmk Community used to be called Raw Edition, and the official version documentation now marks Community releases with a .community suffix. Scripts written for the old names may need updating.

Getting started with PRTG Freeware

1. Install the standard PRTG installer on a dedicated Windows VM. It starts as an evaluation of the full product and falls back to the Freeware edition with 100 sensors.
2. Change the default administrator password at first login and turn on HTTPS.
3. Put Windows credentials on the top-level group once, so every device you add inherits them.
4. Run auto-discovery on a small range, then delete the sensors you do not need before adding more devices. Discovery can use up the budget in minutes.
5. Check the sensor count after every change, and trim the configuration before the evaluation ends, because sensors over the limit stop being monitored.

Remote probes connect back to the core on TCP 23560, so open that port only from the probe networks.

Alerting

PRTG sends notifications by email and push to its mobile apps from notification templates, and you can set dependencies so that a down firewall produces one alert instead of fifty. Checkmk uses notification rules: a local mail system on the server (Postfix with a smarthost is typical) delivers the mail, users get addresses and contact groups, and you test the rule from the notification settings before trusting it. Checkmk takes longer to set up here, but its rules are very flexible once they exist.

Maintenance and updates

Checkmk publishes patch releases with a p number. Per the official documentation, a major version receives bug and security fixes for at least 24 months. Updating means installing the new package next to the old one and running omd update on the site. PRTG updates through its own installer on the Windows core, and Paessler publishes stable builds on a history page you can check before updating.

Limitations of each

Checkmk Community

• It needs Linux, Docker or the appliance, which is a barrier on a pure Windows shop.
• Paid editions add advanced analytics and reporting, more automation, distributed monitoring and professional support; Community has community support only.
• The vendor rates its CPU efficiency below the commercial editions, which matters mostly at larger scale.
• Rule-based configuration takes time to learn if you come from template-based tools.

PRTG Freeware

• The 100-sensor budget covers about ten devices with full coverage.
• The core server is Windows only and the software is proprietary.
• Auto-discovery and flow sensors can fill the budget or load the core quickly.

Other free options in our catalogue

If neither fits, PA Server Monitor Free is a much narrower Windows tool: one server or ten monitors, with event log, ping and web page checks only. For agentless monitoring with network maps, NetCrunch is commercial and has no free edition. For wider automation and runbook tooling around monitoring, see our sysadmin automation tools overview.

How to choose

1. Count your devices and multiply by 5 to 10 sensors. If the total is over 100, PRTG Freeware will not cover you.
2. Look at the host you can dedicate. A Windows VM points to PRTG; a Linux VM or a container host points to Checkmk.
3. Decide who will maintain it. PRTG gets you to graphs faster; Checkmk rewards the admin who will invest in rules and agents.
4. Think about growth. Staying free beyond ten devices is realistic on Checkmk Community and not on PRTG Freeware.
5. Run both for a day on a few hosts if you can. Both are free, and the first impression of the interface is a fair tiebreaker.

FAQ

Is Checkmk Community really free?

Yes. Checkmk Community, formerly Raw Edition, is free and open source under GPL-2.0. The Pro and Ultimate editions are commercial.

What are the Checkmk Community edition limitations?

The vendor sizes it for small infrastructures of about 100 hosts and gives community support only. Advanced analytics and reporting, more automation and distributed monitoring belong to the paid editions.

What are the PRTG free version limitations?

The limit is 100 sensors, which Paessler’s own guidance of 5 to 10 sensors per device turns into about ten devices. The core server also has to run on Windows.

Is there a PRTG free download?

Yes. You install the regular PRTG installer, and the installation falls back to the Freeware edition with 100 sensors once the evaluation ends.

Can I run Checkmk Community in Docker?

Yes. The official image is checkmk/check-mk-community, and it runs a full site in a single container.

Checkmk vs PRTG: which is easier?

PRTG is faster to get running on Windows because of its sensor templates and discovery. Checkmk takes more setup but scales further without a sensor budget.

Last updated: 11 October 2026 · AdminHub Plus editorial team. Licence, version and platform details are checked against each developer's official documentation.