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Cloud · head to head

K3s vs Eclipse Mosquitto

K3s logo

K3s

Cloud

Lightweight certified Kubernetes distribution in a single binary

From
Free
Rated
-
Full reviewWebsite
Eclipse Mosquitto logo

Eclipse Mosquitto

Networking

Small, EPL-licensed MQTT broker that runs on hardware other brokers cannot

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: K3s the SQLite default is single-server only; highly available control planes need etcd or an external datastore, which removes much of the simplicity; Eclipse Mosquitto there is no clustering: Mosquitto is a single process, so high availability means building your own failover and accepting session loss on switchover.
  • They diverge on capability: K3s covers Single binary, Eclipse Mosquitto covers MQTT 5.0 support.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which K3s and Eclipse Mosquitto actually diverge.

Attributes where K3s and Eclipse Mosquitto differ
AttributeK3sEclipse Mosquitto
PlatformsLinux, ARM, Self-hostedLinux, Windows, macOS, Docker
CategoryCloudNetworking

Identical on both: starting price (Free), pricing model (Open source, no licence fee), free tier (Yes), user rating (Not yet rated).

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 K3s

  • Single binary
  • SQLite by default
  • Certified conformant
  • Batteries included
  • Low resource footprint
  • Simple install

Only in Eclipse Mosquitto

  • MQTT 5.0 support
  • Very small footprint
  • Bridging
  • WebSockets listener
  • Command line clients
  • Dynamic security plugin

What people use each for

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

K3s

  • Kubernetes on edge sites and IoT hardware where full clusters will not fitnot Eclipse Mosquitto
  • Development and CI clusters that must start fast and cost nothingnot Eclipse Mosquitto
  • Small production clusters where full Kubernetes is more operations than the workload justifiesnot Eclipse Mosquitto
  • Teaching and learning Kubernetes without cloud spendnot Eclipse Mosquitto

Eclipse Mosquitto

  • A home or building automation stack where the broker must run on the same small computer as everything elsenot K3s
  • An industrial gateway that buffers local telemetry and bridges selected topics to a cloud brokernot K3s
  • Local development and testing of MQTT clients without provisioning a cloud IoT servicenot K3s
  • An air-gapped deployment where a broker with no licence server and no phone-home behaviour is a requirementnot K3s

Where each one falls short

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

K3s

  • The SQLite default is single-server only; highly available control planes need etcd or an external datastore, which removes much of the simplicity
  • Bundled components such as Traefik are opinionated defaults that larger teams often strip out and replace
  • Removed in-tree cloud provider integrations mean cloud-specific features need external controllers
  • Aimed at small and edge clusters, so very large deployments are better served by a standard distribution

Eclipse Mosquitto

  • There is no clustering: Mosquitto is a single process, so high availability means building your own failover and accepting session loss on switchover.
  • Persistence is a local file rather than a replicated store, so a disk failure or an unclean shutdown can lose retained messages and queued QoS traffic.
  • Practical capacity is a few thousand concurrent clients on typical hardware, so a growing device fleet eventually forces a migration to a clustered broker.
  • The Eclipse Public Licence is weak copyleft rather than permissive, which some legal teams treat as a blocker when embedding the broker in a shipped commercial product.
  • There is no commercial support to buy from the project, so production incidents rely on community mailing lists or on paying a third party who happens to know the codebase.

Pricing, plan by plan

K3s

Free
  • K3sFree
    • Full functionality
    • No usage limits
    • Community support

Eclipse Mosquitto

Free
  • Eclipse MosquittoFree
    • Eclipse Public License 2.0 with Eclipse Distribution Licence
    • MQTT 5.0, 3.1.1 and 3.1
    • No client or message limits beyond your hardware

Which should you pick?

Choose K3s if

  • You need single binary.
  • You want to start without paying.
  • You work on Linux, ARM, Self-hosted.
  • You also want sqlite by default.
K3s review

Choose Eclipse Mosquitto if

  • You need mqtt 5.0 support.
  • You want to start without paying.
  • You work on Linux, Windows, macOS, Docker.
  • You also want very small footprint.
Eclipse Mosquitto review

Questions people ask

Is K3s or Eclipse Mosquitto better?
Neither clearly leads. K3s starts at Free and Eclipse Mosquitto at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, K3s or Eclipse Mosquitto?
K3s starts at Free and Eclipse Mosquitto at Free.
Does K3s or Eclipse Mosquitto run on more platforms?
K3s runs on Linux, ARM, Self-hosted. Eclipse Mosquitto runs on Linux, Windows, macOS, Docker.
Can I use K3s for free?
Both have a free tier, so you can try either at no cost before committing.
What is K3s best used for?
K3s is most often used for kubernetes on edge sites and iot hardware where full clusters will not fit, development and ci clusters that must start fast and cost nothing, small production clusters where full kubernetes is more operations than the workload justifies, teaching and learning kubernetes without cloud spend. Of those, kubernetes on edge sites and iot hardware where full clusters will not fit and development and ci clusters that must start fast and cost nothing are not what Eclipse Mosquitto is typically brought in for.
What can K3s do that Eclipse Mosquitto cannot?
K3s covers Single binary, SQLite by default, Certified conformant, Batteries included. Eclipse Mosquitto covers MQTT 5.0 support, Very small footprint, Bridging, WebSockets listener.

Answered from the vendors’ own pages

K3s: Is K3s free?

Yes. K3s is open source with no licence fee. SUSE sells commercial support around Rancher separately.

Eclipse Mosquitto: Can Mosquitto be clustered?

No. It is a single process. High availability requires an external failover arrangement you build yourself.

K3s: Is K3s real Kubernetes?

Yes. It is CNCF-certified conformant, so standard manifests, kubectl and Helm charts work without modification.

Eclipse Mosquitto: What licence is it?

Eclipse Public License 2.0 alongside the Eclipse Distribution License, a weak copyleft rather than a permissive licence.

K3s: Why is K3s smaller than Kubernetes?

It strips legacy, alpha and in-tree cloud provider code, packages everything as one binary, and defaults to SQLite instead of etcd.

Eclipse Mosquitto: How many clients can it handle?

A few thousand concurrent connections on ordinary hardware; beyond that, use a clustered broker.

K3s: Can K3s run in production?

Yes, and it does, particularly at the edge and for small clusters. For a highly available control plane you need to move off the SQLite default to etcd or an external datastore.

Eclipse Mosquitto: Does it support MQTT 5?

Yes, along with 3.1.1 and 3.1.

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