How to Convert Multiple ICNS Files to JXL?
1. Download and Install reaConverter
reaConverter is quick to download, install and launch. This standalone software is extremely efficient in managing a wide range of batch conversions. reaConverter is incredibly powerful and boasts an extensive variety of features.
2. Load your ICNS files
Start reaConverter and load all the .icns files you intend to convert into .jxl. The software supports multiple ICNS conversion and processes all files locally on your computer.
Select ICNSs from a folder or by drag-and-dropping them directly into the reaConverter window.

3. Select JXL as output format
Pick the JXL as output format and choose the destination folder where you want to save new .jxl files.

4. Start ICNS to JXL conversion
Then simply press Convert button and your conversion will begin in no time!

Once the conversion is complete, you can find your JXL files in the destination folder you selected.