As Cura grows in popularity, it incorporates more and more 3D printers.

One downside is that this hurts the start-up time as Cura checks for all available 3D printer definitions before it gets going.

In due time, this will no question be solved with a more complicated start-up routine, but in the meantime, here’s a workaround:

You can simply delete the 3D printer definitions you don’t use.

This will speed up Cura start-up by up to whopping 70%!

(How much will depend on your computer. Slower computers see larger gains. Tested on Mac and PC with Cura 3.0.3)

Delete Unused Cura Printer Definitions

1. Navigate to your Cura installation and locate thedefinitions folder.


  • Go to Applications folder, right click on and select Show Package Contents
  • Navigate to /Applications/[ or Ultimaker]/Contents/Resources/resources/definitions


  • Navigate to C:\Program Files\Cura [your Cura version number]\resources

2. Delete the unused printer definitions.

Delete all files other than

  • fdmextruder.def.json
  • fdmprinter.def.json
  • custom.def.json
  • imade3d_jellybox.def.json

This way you will end up with only 4 files in the definitions folder compared to the 89+ before.)

3. That’s it.

Restart Cura and enjoy your faster start up time 👍

You can always get the definitions back by simply re-installing Cura (or copy-pasting the printer definitions from an alternate .)