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Networking · head to head

OPNsense vs PRTG Network Monitor

OPNsense logo

OPNsense

Networking

FreeBSD-based firewall and routing platform with weekly updates and a full configuration API

From
Free
Rated
-
Full reviewWebsite
PRTG Network Monitor logo

PRTG Network Monitor

Networking

Infrastructure monitoring licensed by sensor count, not by device, which changes what a licence actually covers

From
On request
Rated
-
Full reviewWebsite

The short version

  • Only OPNsense has a free tier, so it costs nothing to try first.
  • Each has a real cost: OPNsense throughput depends entirely on hardware you selected yourself, and intrusion prevention at multi-gigabit rates will saturate a machine that handled plain firewalling fine, with no vendor sizing commitment to fall back on.; PRTG Network Monitor licensing by sensor rather than device means the real cost per device is unpredictable until sensor density is measured; a small network of complex devices can need a much larger tier than device count alone suggests
  • They diverge on capability: OPNsense covers Stateful firewall on pf, PRTG Network Monitor covers Sensor-based monitoring.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which OPNsense and PRTG Network Monitor actually diverge.

Attributes where OPNsense and PRTG Network Monitor differ
AttributeOPNsensePRTG Network Monitor
Starting priceFreeOn request
Pricing modelOpen source, no licence feePer sensor tier, billed monthly on an annual contract
Free tierYesNo
Platformsx86-64 appliances, Virtual machines, Deciso hardwareWindows, Web, iOS, Android

Identical on both: user rating (Not yet rated), category (Networking).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in OPNsense

  • Stateful firewall on pf
  • VPN suite
  • Suricata IDS and IPS
  • Full configuration API
  • High availability
  • Weekly update cadence

Only in PRTG Network Monitor

  • Sensor-based monitoring
  • Auto-discovery
  • Multiple monitoring technologies
  • Maps and dashboards
  • Cloud and hybrid deployment

What people use each for

The jobs each tool is most often brought in to do.

OPNsense

  • Replacing a small business firewall appliance whose renewal quote exceeded the cost of the hardwarenot PRTG Network Monitor
  • Branch offices where the firewall configuration must be produced by Ansible rather than by handnot PRTG Network Monitor
  • Sites that need WireGuard and intrusion prevention on the same box without separate feature licencesnot PRTG Network Monitor
  • A homelab or lab network needing VLAN routing, multi-WAN and DNS filtering on one machinenot PRTG Network Monitor

PRTG Network Monitor

  • An IT team wanting network, server and application monitoring in one product rather than assembling separate open source toolsnot OPNsense
  • An organisation that wants a Windows-installable on-premises monitoring server with a polished UI out of the boxnot OPNsense
  • A team sizing a monitoring purchase that needs to calculate sensor density per device carefully before committing to a tiernot OPNsense
  • A company wanting hybrid on-premises and cloud monitoring from the same licence and dashboardnot OPNsense

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

OPNsense

  • Throughput depends entirely on hardware you selected yourself, and intrusion prevention at multi-gigabit rates will saturate a machine that handled plain firewalling fine, with no vendor sizing commitment to fall back on.
  • The weekly update cadence is good for security but means more change events than a team used to annual appliance firmware, and occasional regressions reach production installations.
  • FreeBSD underneath limits driver support compared with Linux, so recent network cards and some virtualisation drivers can be unsupported or slow.
  • The plugin ecosystem is uneven in quality; some plugins are maintained by a single contributor and can lag a major release, breaking a function you depended on.
  • Community support is a forum, so an outage at two in the morning on the free edition is your problem alone unless you bought the business subscription in advance.

PRTG Network Monitor

  • Licensing by sensor rather than device means the real cost per device is unpredictable until sensor density is measured; a small network of complex devices can need a much larger tier than device count alone suggests
  • Different PRTG licence sizes cannot be combined on one server, so outgrowing a tier means a step change to the next tier rather than a smooth incremental add
  • It requires a Windows server for on-premises deployment, which is an added infrastructure and patching burden compared with a Linux-native open source alternative
  • Pricing is materially higher than open source options like Icinga or LibreNMS for comparable core monitoring capability, and the premium is for polish and support rather than unique functionality
  • The free tier (100 sensors) is limited enough that most real deployments quickly need a paid tier, so it functions more as a trial than a genuinely usable free offering
  • Custom sensor scripting and advanced configuration still require real monitoring expertise; the polished UI does not remove the underlying complexity of correctly instrumenting a large network

Pricing, plan by plan

OPNsense

Free
  • OPNsense Community EditionFree
    • MIT licence with no feature restrictions
    • All VPN, IDS and HA features included
    • Weekly updates and two major releases a year
  • OPNsense Business Edition$undefined/year
    • Stabilised update track lagging community releases
    • Commercial support from Deciso
    • Additional enterprise plugins and configuration backup

PRTG Network Monitor

On request
  • PRTG 500$200/month
    • Up to 500 sensors
  • PRTG 1000$358/month
    • Up to 1,000 sensors
  • PRTG 2500$742/month
    • Up to 2,500 sensors
  • PRTG 5000$1300/month
    • Up to 5,000 sensors

Which should you pick?

Choose OPNsense if

  • You need stateful firewall on pf.
  • You want to start without paying.
  • You work on x86-64 appliances, Virtual machines, Deciso hardware.
  • You also want vpn suite.
OPNsense review

Choose PRTG Network Monitor if

  • You need sensor-based monitoring.
  • You work on Windows, Web, iOS, Android.
  • You also want auto-discovery.
PRTG Network Monitor review

Questions people ask

Is OPNsense or PRTG Network Monitor better?
Neither clearly leads. OPNsense starts at Free and PRTG Network Monitor at On request, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, OPNsense or PRTG Network Monitor?
OPNsense has a free tier; the other does not. Paid plans start at Free for OPNsense and On request for PRTG Network Monitor.
Does OPNsense or PRTG Network Monitor run on more platforms?
OPNsense runs on x86-64 appliances, Virtual machines, Deciso hardware. PRTG Network Monitor runs on Windows, Web, iOS, Android.
Can I use OPNsense for free?
Yes. OPNsense has a free tier, so you can try it without paying. PRTG Network Monitor starts at On request.
What is OPNsense best used for?
OPNsense is most often used for replacing a small business firewall appliance whose renewal quote exceeded the cost of the hardware, branch offices where the firewall configuration must be produced by ansible rather than by hand, sites that need wireguard and intrusion prevention on the same box without separate feature licences, a homelab or lab network needing vlan routing, multi-wan and dns filtering on one machine. Of those, replacing a small business firewall appliance whose renewal quote exceeded the cost of the hardware and branch offices where the firewall configuration must be produced by ansible rather than by hand are not what PRTG Network Monitor is typically brought in for.
What can OPNsense do that PRTG Network Monitor cannot?
OPNsense covers Stateful firewall on pf, VPN suite, Suricata IDS and IPS, Full configuration API. PRTG Network Monitor covers Sensor-based monitoring, Auto-discovery, Multiple monitoring technologies, Maps and dashboards.

Answered from the vendors’ own pages

OPNsense: How is it different from pfSense?

It is a 2015 fork with an MIT licence, a fixed weekly release cadence, a complete configuration API and a different interface. Feature coverage is comparable; the release process and API are the real differences.

PRTG Network Monitor: Is PRTG licensed per device or per sensor?

Per sensor. Each individually monitored metric counts as one sensor, so a single device is typically several sensors.

OPNsense: Do I need the Business Edition?

Only if you want commercial support or a slower, stabilised update stream. No features are withheld from the community edition.

PRTG Network Monitor: Can I combine two PRTG licence tiers on one server?

No, Paessler states different license sizes cannot be combined on one PRTG installation.

OPNsense: Can it handle a gigabit internet connection?

Plain firewalling on modest current hardware, comfortably. With Suricata inspection enabled, expect to need a considerably stronger CPU.

PRTG Network Monitor: Is there a free tier?

Yes, PRTG offers a free tier limited to 100 sensors, which most production networks will exceed quickly.

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