Softwr

Networking · head to head

OPNsense vs Prometheus

OPNsense logo

OPNsense

Networking

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

From
Free
Rated
-
Full reviewWebsite
Prometheus logo

Prometheus

Networking

Open source monitoring and alerting toolkit for cloud native environments

From
Free
Rated
-
Full reviewWebsite

The short version

  • 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.; Prometheus not suitable for per-request billing as collected data lacks 100% accuracy
  • They diverge on capability: OPNsense covers Stateful firewall on pf, Prometheus covers Multi-dimensional Data Model.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which OPNsense and Prometheus actually diverge.

Attributes where OPNsense and Prometheus differ
AttributeOPNsensePrometheus
Pricing modelOpen source, no licence feeopen-source
Platformsx86-64 appliances, Virtual machines, Deciso hardwareLinux, macOS, Windows
FoundedUnknown2015

Identical on both: starting price (Free), free tier (Yes), 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 Prometheus

  • Multi-dimensional Data Model
  • PromQL Query Language
  • Pull-based Collection
  • Service Discovery
  • Alerting Rules
  • Federation
  • Local Storage
  • Grafana

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 Prometheus
  • Branch offices where the firewall configuration must be produced by Ansible rather than by handnot Prometheus
  • Sites that need WireGuard and intrusion prevention on the same box without separate feature licencesnot Prometheus
  • A homelab or lab network needing VLAN routing, multi-WAN and DNS filtering on one machinenot Prometheus

Prometheus

  • Monitoring and alerting systemnot OPNsense
  • Time-series databasenot OPNsense
  • Infrastructure metrics collectionnot 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.

Prometheus

  • Not suitable for per-request billing as collected data lacks 100% accuracy
  • Hard limit on scrape body size; large responses cause scrape failure
  • Per-scrape sample limit enforced; exceeding limit marks targets as failed
  • Not designed for long-term durable storage; optimised for metrics collection

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

Prometheus

Free
  • Prometheus (Open Source)Free
    • 100% open source
    • Community-driven project
    • Apache 2 License

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 Prometheus if

  • You need multi-dimensional data model.
  • You want to start without paying.
  • You work on Linux, macOS, Windows.
  • You also want promql query language.
Prometheus review

Questions people ask

Is OPNsense or Prometheus better?
Neither clearly leads. OPNsense starts at Free and Prometheus at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, OPNsense or Prometheus?
OPNsense starts at Free and Prometheus at Free.
Does OPNsense or Prometheus run on more platforms?
OPNsense runs on x86-64 appliances, Virtual machines, Deciso hardware. Prometheus runs on Linux, macOS, Windows.
Can I use OPNsense for free?
Both have a free tier, so you can try either at no cost before committing.
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 Prometheus is typically brought in for.
What can OPNsense do that Prometheus cannot?
OPNsense covers Stateful firewall on pf, VPN suite, Suricata IDS and IPS, Full configuration API. Prometheus covers Multi-dimensional Data Model, PromQL Query Language, Pull-based Collection, Service Discovery.

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.

Prometheus: What does Prometheus cost?

Prometheus is completely free and open source. There are no pricing tiers or paid plans. The entire project is licensed under Apache 2 and hosted on GitHub.

Source
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.

Prometheus: Is Prometheus commercial software or free?

Prometheus is 100% open source and community-driven. It is a CNCF graduated project with no commercial restrictions or licensing fees.

Source
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.

Prometheus: How is Prometheus licensed?

Prometheus is licensed under the Apache 2 License, which permits free use, modification, and distribution for commercial and non-commercial purposes.

Source
Share

Related pages

More on OPNsense

More on Prometheus

Keep looking

Other head to heads