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Databases · head to head

EMQX vs Kepware Server

EMQX logo

EMQX

Databases

Erlang MQTT broker for large IoT fleets, relicensed to BSL with production free use limited to one node

From
Free
Rated
-
Full reviewWebsite
Kepware Server logo

Kepware Server

Manufacturing

Industrial connectivity server translating 150-plus PLC protocols into OPC UA, formerly KEPServerEX

From
On request
Rated
-
Full reviewWebsite

The short version

  • Only EMQX has a free tier, so it costs nothing to try first.
  • Each has a real cost: EMQX the move to Business Source Licence 1.1 at version 5.9 in May 2025 limits free production use to a single node, so the clustering that justifies choosing EMQX now requires a paid subscription from the second node onward.; Kepware Server the base server is the small part of the bill; driver suites are priced by protocol family, and a mixed-vendor plant buys several, which is how a connectivity layer alone reaches tens of thousands of dollars.
  • They diverge on capability: EMQX covers Erlang clustering, Kepware Server covers 150-plus device drivers.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which EMQX and Kepware Server actually diverge.

Attributes where EMQX and Kepware Server differ
AttributeEMQXKepware Server
Starting priceFreeOn request
Pricing modelPer month by connection and session volumequote
Free tierYesNo
PlatformsLinux, Docker, Kubernetes, Cloud, macOSWindows, Linux
CategoryDatabasesManufacturing

Identical on both: 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 EMQX

  • Erlang clustering
  • MQTT 5.0 and QUIC
  • Rule engine
  • Data integration sinks
  • Session persistence
  • Multi protocol gateways
  • Authentication and authorisation
  • Dashboard and REST API

Only in Kepware Server

  • 150-plus device drivers
  • OPC UA server
  • IoT Gateway
  • DataLogger
  • Redundancy Master
  • Security Policies
  • Configuration API
  • Kepware Edge

What people use each for

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

EMQX

  • A connected vehicle platform needing millions of persistent MQTT sessions with QUIC for handover across mobile networksnot Kepware Server
  • An industrial operator routing sensor telemetry straight into TimescaleDB or Kafka without writing a consumer servicenot Kepware Server
  • An IoT product team that has outgrown a single Mosquitto instance and needs clustering and shared subscriptionsnot Kepware Server
  • A smart building deployment mixing MQTT, CoAP and LwM2M devices on one brokernot Kepware Server

Kepware Server

  • Feeding a historian from a mixed plant of Allen-Bradley and Siemens PLCs without writing per-protocol driversnot EMQX
  • Publishing CNC machine state from FANUC and Haas controls to an OEE system over MQTTnot EMQX
  • Bridging legacy serial Modbus devices into an OPC UA architecture during a phased controller replacementnot EMQX
  • Running redundant collection servers so a cloud analytics pipeline does not lose data during Windows patchingnot EMQX

Where each one falls short

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

EMQX

  • The move to Business Source Licence 1.1 at version 5.9 in May 2025 limits free production use to a single node, so the clustering that justifies choosing EMQX now requires a paid subscription from the second node onward.
  • The relicensing arrived in a minor release, which caught users who had pinned to 5.x expecting Apache 2.0 terms and forced legal review of existing deployments.
  • Running an Erlang/OTP cluster well requires operational knowledge most teams do not have, and diagnosing distribution, mnesia or memory issues means learning a runtime you use for nothing else.
  • Enterprise pricing is quoted rather than published for the self-managed edition, so the cost of the clustered configuration you actually need is invisible until you talk to sales.
  • The Serverless tier caps at around a thousand connections and shares infrastructure, which makes it a prototyping tier rather than a genuine small production option.

Kepware Server

  • The base server is the small part of the bill; driver suites are priced by protocol family, and a mixed-vendor plant buys several, which is how a connectivity layer alone reaches tens of thousands of dollars.
  • KEPServerEX to Kepware Server 7 is a migration rather than an in-place upgrade, and driver entitlements do not always transfer cleanly, so budget for revalidating every channel.
  • The full driver portfolio is Windows-only; the Linux product, Kepware Edge, supports a subset of drivers and is subscription-licensed by tag count, so an edge-first architecture cannot simply reuse the Windows configuration.
  • Three names have been in circulation for the same lineage, and quotes, forum answers and integrator experience still mix KEPServerEX, ThingWorx Kepware Server and Kepware Server, which produces mismatched proposals.
  • It is a translation layer with no storage, contextualisation or visualisation of its own, so it is always an addition to a historian or platform purchase rather than a substitute for one.

Pricing, plan by plan

EMQX

Free
  • Open Source single nodeFree
    • BSL 1.1 licence since version 5.9
    • Free production use of one node only
    • All former enterprise features visible
  • ServerlessFree
    • Free monthly quota then pay as you go
    • Up to 1,000 connections
    • 8 by 5 support
  • Dedicated Flex$234/month
    • Single tenant cluster
    • Traffic allowance included
    • 24/7 support
  • Enterprise self-managed$undefined/year
    • Deploy on premises, at the edge or in any cloud
    • Clustering licensed
    • 256 MB maximum message size

Kepware Server

On request
  • Kepware Server$undefined/year
    • Base server as a perpetual licence with annual maintenance, or subscription
    • Driver suites priced by protocol family and bought separately from the server
    • Advanced plug-ins such as IoT Gateway, DataLogger and Redundancy Master licensed individually

Which should you pick?

Choose EMQX if

  • You need erlang clustering.
  • You want to start without paying.
  • You work on Linux, Docker, Kubernetes, Cloud, macOS.
  • You also want mqtt 5.0 and quic.
EMQX review

Choose Kepware Server if

  • You need 150-plus device drivers.
  • You work on Windows, Linux.
  • You also want opc ua server.
Kepware Server review

Questions people ask

Is EMQX or Kepware Server better?
Neither clearly leads. EMQX starts at Free and Kepware Server at On request, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, EMQX or Kepware Server?
EMQX has a free tier; the other does not. Paid plans start at Free for EMQX and On request for Kepware Server.
Does EMQX or Kepware Server run on more platforms?
EMQX runs on Linux, Docker, Kubernetes, Cloud, macOS. Kepware Server runs on Windows, Linux.
Can I use EMQX for free?
Yes. EMQX has a free tier, so you can try it without paying. Kepware Server starts at On request.
What is EMQX best used for?
EMQX is most often used for a connected vehicle platform needing millions of persistent mqtt sessions with quic for handover across mobile networks, an industrial operator routing sensor telemetry straight into timescaledb or kafka without writing a consumer service, an iot product team that has outgrown a single mosquitto instance and needs clustering and shared subscriptions, a smart building deployment mixing mqtt, coap and lwm2m devices on one broker. Of those, a connected vehicle platform needing millions of persistent mqtt sessions with quic for handover across mobile networks and an industrial operator routing sensor telemetry straight into timescaledb or kafka without writing a consumer service are not what Kepware Server is typically brought in for.
What can EMQX do that Kepware Server cannot?
EMQX covers Erlang clustering, MQTT 5.0 and QUIC, Rule engine, Data integration sinks. Kepware Server covers 150-plus device drivers, OPC UA server, IoT Gateway, DataLogger.

Answered from the vendors’ own pages

EMQX: Is EMQX still open source?

Not in the OSI sense since version 5.9. It is source-available under Business Source Licence 1.1, reverting to Apache 2.0 four years after each release.

Kepware Server: Is KEPServerEX discontinued?

The name is. KEPServerEX and ThingWorx Kepware Server have been unified into Kepware Server, currently version 7, and the older names are being retired.

EMQX: Can I run a free cluster?

No. The additional use grant permits free production use of one node; clustering requires a commercial licence.

Kepware Server: Is a perpetual licence still available?

Yes for the Windows server, with annual maintenance. Kepware Edge on Linux is subscription-only.

EMQX: What changed for existing users?

Community and enterprise editions merged, so all features are now visible, but the licence terms tightened in the same minor release.

Kepware Server: What drives the price?

The number and type of driver suites, not the number of tags on the Windows product. Kepware Edge is priced by tag count.

EMQX: Which version is still Apache 2.0?

Releases before 5.9 remain under Apache 2.0, and each BSL release converts to Apache 2.0 four years after publication.

Kepware Server: Can I evaluate it before buying?

Yes. The runtime works for two hours at a time without a licence, indefinitely, which is enough to prove connectivity but not to run production.

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