How to change Default Properties File Encoding to UTF-8

Problem

Default Properties File Encoding is set to ISO-8859-1 when it should be UTF-8.

Cause

In IntelliJ IDEA 2025.3 and earlier, the default properties file encoding is ISO-8859-1. A change of this default to UTF-8 caused performance problems and was reverted.

Resolution

Update to IntelliJ IDEA 2026.1 or later. From 2026.1, the IDE detects the encoding of properties files automatically (IJ detect ISO 8859-1 for properties files instead of using UTF-8 as default property encoding for Java 9 and higher ).

Workaround for IntelliJ IDEA 2025.3 and earlier

To make UTF-8 the default properties file encoding, follow these steps:

1. Press Shift twice to open the Search Everywhere dialog.
2. Type Registry... and press Enter.
3. Locate the setting named properties.file.encoding.legacy.support and ensure it is unchecked.
4. Restart IntelliJ IDEA to apply the configuration change.

This adjustment sets UTF-8 as the default encoding for properties files.