The file size limit is 40MB. If your file is larger, you will not be able to upload into Turnitin and will see the error message Your submission exceeds the maximum allowed size.

Files are usually this large because they contain high quality images. This post from the Microsoft Office help guide explains how to compress images in Word, Powerpoint and Excel files on a PC (or how to do this on a Mac).

You can also reduce the file size by saving it as a PDF file. This Microsoft Office help guide explains how to save as PDF. Please note that uploading PDF files created from other programmes often results in a different error message as Turnitin is unable to read the file.