If you are unfortunate enough to be running OS X Catalina (and you have my sympathy) getting UECIDE to run properly can be a bit of a chore. Catalina is the last version of OS X where UECIDE will be officially supported, and even then it's certainly not a recommended system to run UECIDE on.

Java Version

UECIDE is a Java application. Catalina comes, by default, with Apple's own implementation of Java installed which, quite simply, does not work. So the first thing you really must do is ditch that in favour of a proper Oracle version. However, as of the time of writing this, Oracle state:

Changes introduced with macOS 10.15 (Catalina) cause certain Java applications to behave incorrectly. Therefore, we cannot certify any JDK version on macOS 10.15 yet.

But you can manually install OpenJDK 14, which:

... is the first release that complies with the new macOS 10.15 hardening and notarization requirements.

Here's how you do it.

  1. Download openjdk-14.0.1_osx-x64_bin.tar.gz
  2. Extract the contents (a folder called jdk-14.jdk)
  3. Move (or copy) that folder into /Library/Java/JavaVirtualMachines/

To test it, from a terminal, run:


It should respond:


Graphical Corruption

The next problem you may encounter is graphical corruption. The default theme does not play well with Catalina, so changing that theme to something else may improve your quality of life somewhat. The biggest telltale of this happening is that windows open as a plain grey box. One of these is, of course, Preferences, which makes it rather hard to change the theme. However there are ways around it. Both of these must be done while UECIDE is not loaded.

From a terminal

Run the command:

/Applications/ --set=theme.laf=systemdefault

That should change the theme for the next time that UECIDE is run. If that doesn't work:

Editing your preferences.txt

Your preferences.txt file is located in your Library/uecide folder. You can edit it with any simple text editor. Look for the line that starts:


and change it to:


Save and exit, and next time UECIDE starts it should have a different theme.

Compilers not working

Catalina has completely dropped all support for 32-bit binaries. If a compiler only has a 32-bit version (such as the chipKIT compiler, although a new version is due soon) it will not work. There is absolutely nothing you can do about that other than wait for the upstream core provider to create a 64-bit version of the compiler.