PPTX file is a Microsoft PPT (.ppm) file that Microsoft uses to display PowerPoint slides in PowerPoint presentations. Windows View Microsoft PowerPoint and PPTX file with Microsoft PowerPoint Viewer If you know of any PPTX file viewer apps for Windows in the Market, please let me know via comment. Other PPTX file viewers for Windows Below are some free file viewers available for Windows. View Microsoft PowerPoint and PPTX file with Microsoft PowerPoint Viewer View Online PowerPoint Viewer for Windows View Online Microsoft PowerPoint Viewer How to view Microsoft PowerPoint Online or PowerPoint online? If you are using Internet Explorer or Mozilla Firefox, you can view PPT files using the free download from above. However, if you need to view files inside Office products on your Windows computer or on macOS with PPTX or Preview, you will have to install or use a paid software to save your files from PowerPoint online. What is the difference between PowerPoint Online and Office PowerPoint Online? Microsoft PowerPoint: View PowerPoint documents online in your browser or download a portable version for later viewing on a mobile device Office PowerPoint Online: A browser based application that helps you view, edit and work with PowerPoint documents online on your computer. No need to install any program or third party software. PowerPoint has been redesigned to be open and responsive for both desktop and touch devices. Microsoft PowerPoint Online has a lot of features, so we recommend going through this information about them to know more: What is the difference between Microsoft PowerPoint Online and Office PowerPoint Online? Microsoft Office PowerPoint Online is an online version of the program that requires no installation and is fully responsive to mouse and touch. The application has multiple tools and functions that allows you to open and view PowerPoint presentations online. Office PowerPoint Online comes with a lot of features, so we recommend going through this information about them to know more: Microsoft PowerPoint Online can save the content and slides in .PPT files. Please note, some above information has changed.