This article explains what an XLL file is and how to open it on your computer.
How do I fix the issue of file format or file extension not valid in Excel?
A file with the XLL file extension is an Excel Add-in file. These files provide a way to use third-party tools and features in Microsoft Excel that are not natively included with the software.
Excel add-ins are similar to DLL files, but they are created specifically for Excel.
XLL files can be opened with Microsoft Excel.
