openHAB 4.0 Milestone Builds

Dear community,

You had to wait for a long while, but I am now happy to announce that we have the first milestone build of openHAB 4.0 ready for download!

There has been a major technical change by moving from Java11 to Java17, which involved upgrading many libraries to very recent versions. This is all successfully done and the snapshot builds were already tested by many of you, which helped on identifying and fixing regressions.
The positive effect is that we are now on a very future-proof technical foundation again and that all contributors can make use of modern language features that Java17 brings.
The downside is that we have to ask you to update your JVM to Java17, if you haven’t done so yet.

Another effect of Java17 is that it does not include the Nashorn Javascript engine anymore, since the GraalVM is the more modern approach in the Java ecosystem.

Please note therefore a couple of changes with regards to Javascript support in openHAB:

  • The application/javascript MIME type has moved from NashornJS to GraalJS due to the removal of NashornJS in Java 14. All UI-based JavaScript scripts including Blocklies are broken now. To make them work again:
    • Migrate your Blocklies (see Rules Blockly | openHAB)
    • Install the JavaScript Nashorn add-on and change the MIME type of your old application/javascript scripts to application/javascript;version=ECMAScript-5.1. The UI has a picker for the MIME type of existing scripts inside the „Script Details“ menu inside the script editor. (Or rewrite them for GraalJS, where the openhab-js library will ease your life.)
  • The JS transformation no longer exists and the SCRIPT transformation should be used instead. Inline JS scripts in transformations and JS profiles are still work in progress.

Besides these things, there was a lot of work on new features and other fixes - see the extensive list on the official release notes.

I have created a new discussion topic for any questions and issues you might have around this first - and all future - openHAB 4.0 Milestone build.



Hi all,

We have reached another milestone on our way to openHAB 4: Please find openHAB 4.0.0.M2 available on our download page and in the Linux package repos! It has quite a long list of fixes and enhancements over the first milestone, see Release openHAB 4.0.0 Milestone 2 · openhab/openhab-distro · GitHub.

As usual, please keep using the existing thread for discussions about the milestone. Thanks!


We have just published the next milestone (number 3) for openHAB 4.0.0!

Please note that there is a breaking change wrt units of measurement - so before doing the update, please read the section in the release notes about this carefully.

If you have any questions or issues, please use the the usual thread for this.



since it is end of June by now, you might be expecting the openHAB 4 release any time soon, right? After all, it is now exactly 6 months after (and before!) christmas.

I’d therefore like to give you a short update: We have decided to slightly postpone the release as we wanted certain features to be finished and included in the release. Our schedule therefore looks like this:

  • July 2: 4.0.0.M4
  • July 16: 4.0.0.M5 (feature freeze)
  • July 21: 4.0.0.RC1 (code freeze)
  • July 23: 4.0.0 GA

So you only need to wait 4 weeks and you will see the new release. And as always: Please help testing the milestones and the release candidate on the way, so that potential issues can be found early on.


According to the schedule above, we have just published openHAB 4.0.0.M4 - please find the release notes on GitHub.
As we are getting close to the final release, please help testing and provide your feedback (especially on regressions) here.


We have reached the very last milestone and with it the feature freeze! Here it is: Release openHAB 4.0.0 Milestone 5 · openhab/openhab-distro · GitHub

With only one more week to go, we will focus on final bug fixes. I think everything looks good so far for shipping another stable and valuable release!


Ok, activity is slowly coming to an end - since milestone 5 we had a few fixes merged and we are happy to have our first release candidate ready! Please see the changes that were done since the last milestone in the release notes on GitHub. If all goes well, this is what we will ship on Sunday as the GA release.
If you find any critical bugs in the RC1, please report them asap here.


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