Alternatives / Paessler PRTG Monitor
Looking for an open source Paessler PRTG alternative? We compared 6 open source monitoring tools by license, discovery, scalability, and maintenance. They cover servers, networks, and applications, with different strengths: Netdata for real-time metrics, Zabbix and Checkmk for broad monitoring, and Scanopy for network documentation.
Written by Maxime DERAME
Last updated:
| Alternative | Best for | License |
|---|---|---|
| Netdata | Real-time metrics with little configuration | GPL-3.0 |
| Scanopy | Self-updating network maps and inventories | AGPL-3.0 |
| Zabbix | Broad monitoring with no per-device fees | AGPL-3.0 |
| Checkmk | Plugin-rich monitoring with a free Raw edition | GPL-2.0 (Raw Edition) |
| Icinga | Custom checks and high availability | GPL-3.0 |
| Nagios | Long-established plugin-based monitoring | GPL-2.0 |
We looked for open-source tools that replace PRTG's job: discovering devices, monitoring availability and performance with sensors or checks, and alerting. We verified each project's license, recent activity, stars, and self-hosting in its repository. Scanopy maps your network instead of monitoring metrics. See our methodology for the full criteria.
Scanopy discovers your network with SNMP, LLDP, and ARP and builds topology diagrams, host inventories, and dependency maps. It does not collect performance metrics or alert, so pair it with a monitoring tool.
Zabbix is the closest in scope: it monitors networks, servers, cloud, and IoT with automated discovery, multitenancy, and no per-device licensing. Checkmk adds automated discovery and over 2,000 plugins, and Netdata gives real-time dashboards with little configuration.
Icinga offers custom checks, fast alerting, multi-tenancy, and high availability, and Nagios is the long-established tool with a plugin architecture and a large library of community add-ons, with Nagios XI as an optional paid product.
Checkmk's free Raw edition is open source, while Enterprise, Cloud, and MSP editions are commercial. Netdata offers a paid cloud service alongside the open-source agent. Scanopy has paid tiers for the hosted service.
Netdata and Icinga are GPL-3.0. Checkmk and Nagios Core are GPL-2.0. Zabbix and Scanopy are AGPL-3.0.
All except Nagios Core had commits within days of this update. Nagios Core's last commit was in August 2026.
PRTG is a proprietary Windows-based product licensed by number of sensors, so costs rise as you monitor more. Open-source monitoring tools have no per-sensor pricing, run on Linux, and have large plugin ecosystems, at the cost of more configuration and, in some cases, a paid support or enterprise edition.
Netdata is a real-time monitoring tool with per-second metrics, zero-configuration dashboards, intelligent alerting, and extensibility for servers, containers, and distributed systems.
Pricing: Free and open source agent; paid cloud and enterprise plans for centralized features.
Zabbix is a full-scale monitoring platform for networks, servers, cloud, and IoT with automated discovery, webhooks, multi-tenancy, log monitoring, and real-time alerting, without per-device licensing.
Pricing: Free; fixed-cost commercial support available.
Scanopy is an AGPL-3.0 network discovery tool that scans with SNMP, LLDP, and ARP, then builds topology diagrams, host inventories, and service dependency maps that update themselves. It documents your network rather than monitoring metrics, and paid tiers exist for the hosted and larger deployments.
Pricing: Free to self-host with limits; paid tiers available.
Checkmk is IT infrastructure monitoring with 2,000+ plugins, automated discovery and configuration, granular alerting, and dashboards. The Raw Edition is open source, and Enterprise, Cloud, and MSP editions are commercial.
Pricing: Free Raw Edition; paid Enterprise, Cloud, and MSP editions.
Icinga is a monitoring platform with real-time checks, custom check configurations, fast alerting, multi-tenancy, and high availability for on-premises, cloud, and hybrid environments.
Pricing: Free; commercial support available.
Nagios Core is a long-established monitoring system for servers, networks, and applications with a powerful plugin architecture, official plugins, and hundreds of community add-ons.
Pricing: Free and open source; commercial editions are separate.
| Alternative | Type | License | Discovery | Best for |
|---|---|---|---|---|
| Netdata | Metrics monitoring | GPL-3.0 | Auto-detect | Servers and containers |
| Scanopy | Network discovery | AGPL-3.0 | SNMP, LLDP, ARP | Network documentation |
| Zabbix | Monitoring platform | AGPL-3.0 | Automated | Mixed IT and OT estates |
| Checkmk | Monitoring platform | GPL-2.0 (Raw edition) | Automated | Mid-sized environments |
| Icinga | Monitoring platform | GPL-3.0 | Manual and API | Multi-tenant setups |
| Nagios | Monitoring platform | GPL-2.0 | Manual | Teams already using Nagios |
Want the broadest PRTG-like monitoring with no sensor fees
Zabbix covers networks, servers, cloud, and IoT with automated discovery and multitenancy.
Want real-time dashboards quickly
Netdata starts collecting metrics with almost no configuration and shows them in real time.
Want automated discovery with a free edition
Checkmk's Raw edition is free and open source with automated discovery and 2,000+ plugins.
Want to document your network
Scanopy builds topology diagrams and inventories from SNMP, LLDP, and ARP, but does not monitor metrics.