Xcode 10, could not decode input file using specific encoding

Find your Localizable.strings in a Terminal and execute:

$ iconv -f UTF-16LE -t UTF-8 Localizable.strings >  LocalizableNew.strings

Then check LocalizableNews.string and if there is no errors just replace files

$ move LocalizableNew.strings Localizable.strings

I have similar error once i open my project in Xcode 10.4 and open it agian in Xcode 10.1.

I solved it by selecting my all Localizable.strings file and change there text encoding to UTF-16(In my case error was related to UTF-16 you can change it to UTF-8)

So changing the text encoding to UTF-16 or UTF-8 will works.

It sounds like the file is corrupted, probably with parts of it encoded in UTF-8 and parts of it encoded in 8859-5. From its name, I would suspect this is a Cyrillic localization (perhaps Russian), and the file was probably edited using an editor that didn't correctly maintain encoding or use UTF-8 (the most common cause of that is editing on Windows).

You'll need to open the file, probably in an external editor that can handle random encodings like vim or Sublime Text, and fix any corruption. Exactly how to do that depends on the nature of the corruption.