In every version of windows over the last 10 years including Windows 7, Microsoft has a habit of hiding file extensions in order to prevent the average user from accidentally renaming a file to an unknown file type. Windows 8 is no exception to this rule, so if you want to easily edit a file’s extension, you’ll have to change a setting to make it visible.
In desktop mode open up Windows Explorer.
Select the View tab from the Explorer ribbon and select Options >> Change folder and search options.
In the Folder Options window click the View tab and then uncheck the box labeled “Hide extensions for known file types.”
Tip: While you’re here, you might also want to change the Hidden files and folders bullet to “Show hidden files, folders, and drives.”
Now file extensions will show after the file name for commonly used file types.