PRTG Freeware

PRTG Freeware is the free edition of Paessler’s PRTG Network Monitor: the same Windows-based monitoring software that larger companies pay for, limited to 100 sensors and free for life. It suits small offices, labs, home networks and admins who want to monitor a handful of servers, switches and internet links with real graphs and alerts. A PRTG free download is the regular installer; when the evaluation period of the full product ends, the installation falls back to the Freeware edition instead of stopping.

The catch is the unit of counting. PRTG does not count devices but sensors, and each sensor is one measurement: a ping, a switch port, a disk, a CPU, a service, an HTTP check. Paessler estimates 5 to 10 sensors per device for full coverage, so 100 sensors realistically covers about ten devices.

PRTG Freeware at a glance

What it does

• Auto-discovers devices in IP ranges and suggests sensors based on device templates.
• Monitors availability and performance with ping, SNMP, WMI, SSH, HTTP/HTTPS, DNS, SMTP and many other sensor types, including hardware health over vendor protocols.
• Measures bandwidth through SNMP traffic sensors and flow sensors (NetFlow, sFlow, jFlow).
• Sends alerts by email, push notification to the PRTG mobile apps, and other notification methods, with thresholds and dependencies to avoid alert storms.
• Builds maps and dashboards, and produces scheduled reports from historical data.
• Recent stable releases keep adding sensors; 26.3.124 brought, for example, an updated FTP Server File Count sensor and a Redfish Fan Status sensor.

How sysadmins use it

Spend the 100 sensors wisely

1. Decide what matters: internet uplink, firewall, core switch uplinks, the hypervisor, key VMs, backup NAS.
2. Remember that the local probe device and its health sensors also count toward the limit.
3. Run auto-discovery on a small range first, then delete sensors you do not need (unused switch ports, duplicate pings) before adding more devices.
4. Check the sensor count in the license information page after every change.

Add a Windows server with credentials

1. Open the group’s Settings and fill in the credentials for Windows systems (a domain account with WMI rights); devices in the group inherit them.
2. Add the device by IP or DNS name, or right-click the group and choose Run Auto-Discovery.
3. Keep the CPU, memory, free disk space and the services that matter; remove the rest.

Get alerts that people read

1. Create a notification template under Setup > Account Settings > Notification Templates (for example email to the IT mailbox and push to the on-call phone).
2. Attach it to Down states at group level so new devices inherit it.
3. Set the dependency of devices behind a firewall or VPN on the ping sensor of that firewall, so one outage produces one alert.

Install and first run

Core server. Windows only: Windows Server 2016, 2019, 2022 or 2025, or Windows 10/11 for small setups. You need .NET Framework 4.7.2 or later (4.8 recommended for new installs). For up to 500 sensors Paessler recommends 4 CPU cores, 4 GB RAM and at least 100 GB of free disk, which is more than enough for 100 sensors. Use a dedicated VM rather than a domain controller or busy file server.

Linux. The core server does not run on Linux. Paessler offers multi-platform probes for Ubuntu, Debian, RHEL and Raspberry Pi OS that collect data and report to a Windows core.

Gotchas.

• The web interface uses HTTP/HTTPS on the core server (ports 80/443 by default); open them in Windows Firewall only for the networks that need access.
• Remote probes connect to the core on TCP 23560.
• Change the default administrator password at first login and enable HTTPS with a proper certificate.
• WMI sensors need Remote WMI/RPC allowed on the targets; for Linux use SSH sensors or SNMP.
• When the evaluation ends, sensors above the 100 limit are no longer monitored; trim the configuration before that point.

Limitations

• 100 sensors in total, which means roughly ten fully monitored devices.
• The core server is Windows-only.
• Proprietary software: free to use within the limit, but not open source.
• Auto-discovery can create many sensors at once and use up the allowance in minutes.
• Frequent scanning intervals and flow sensors put load on the core; keep defaults unless you need tighter checks.

PRTG vs alternatives

FAQ

Is PRTG free?

Yes, up to 100 sensors. Paessler calls this the Freeware edition and states it is free for life; more sensors require a paid licence.

What are the PRTG free version limitations?

The main limit is 100 sensors, about ten devices with full coverage. The core server must run on Windows.

How do I get the PRTG freeware edition download?

Install the standard PRTG Network Monitor installer. It starts as an evaluation of the full product and reverts to the Freeware edition with 100 sensors afterwards.

Can PRTG run on Linux?

The core server cannot. Linux machines can host multi-platform probes that report to a Windows core, and PRTG can monitor Linux hosts over SSH and SNMP.

PRTG vs Zabbix: which should I choose?

PRTG is faster to set up on Windows and polished out of the box but limited to 100 sensors for free. Zabbix is fully open source with no limits but needs more Linux and configuration work.

What are good open-source alternatives to PRTG?

Checkmk Community, Zabbix and LibreNMS are the common choices; all run on Linux.

Is there a PRTG desktop app?

Yes. Besides the web interface and the iOS and Android apps, Paessler offers the PRTG app for desktop (known as PRTG Desktop) for Windows and macOS. With freeware or trial servers it connects to at most two of them at the same time.

Last checked against official sources: 1 October 2026 (developer website: paessler.com). Versions and licence terms change — confirm on the developer's site before deploying in production.