autoNormalize is an advanced folder setting that affects the handling of files with incorrect UTF-8 normalization in their name. When set, such files are renamed to the correctly normalized form during scanning.


This option should normally be set to true.


File names can be represented in many different ways. Some systems use an extended ASCII character set like ISO-8859-1 (Latin), others may use a different encoding to represent Chinese, Russian and so on. The modern standard is to use Unicode in UTF-8 encoding, even when the file system itself doesn’t dictate a format, such as is the case on most Unix-like systems. Syncthing will refuse to synchronize files with names not encoded in UTF-8.

However, there are different ways of encoding the same character even within UTF-8. These are called normalization forms and differ primarily between Mac and everything else. Differences in normalization form means that you could on some systems have three (or more) files all called räksmörgås.txt, räksmörgås.txt, and räksmörgås.txt – those are the same characters, but expressed in different ways. More commonly an issue arises when files are copied from a system that uses one normalization form (Mac) to a system using another normalization form (Windows) without translation; say, via a USB stick.

To avoid such issues, Syncthing automatically corrects normalization errors when it runs into them, unless this option is disabled.