err is: Err extension is related to Error log file. You can try to open err files Note Pad application on your computer.
Some softwares record the errors in writing. FoxPro is one of the most popular software that creates ERR files. You won`t need any extra software to open err files. You have chance to open these with Note Pad application on your computer.
Err File format viewers or openers
Err File related links.