Source: WebAIM
PowerPoint is a good format for face to face presentations, but it is usually not the best format for content on the web. The file can be large, and users must either have Microsoft Office or a special plugin in order to view the file. One of the following formats may provide a better alternative.
Export to PDF
PDF is often the best format to display PowerPoint presentations on the web. The file size is relatively small, distracting slide transitions are removed, and everyone has a PDF reader. Most importantly, heading structure and other accessibility information will remain intact if you export the file correctly. If you have a presentation with tables, and if you know how to add additional accessibility information in Adobe Acrobat, it might be possible to create a PDF file that is more accessible than the original PPT file.
Create HTML slides or outline
Source: WebAIM
Important
Many versions of PowerPoint have a Save As Web Page option. It does not create accessible HTML content and should be avoided.
If you are comfortable with HTML and CSS, and if your content is intended to be displayed on the web, you could consider creating your own slides in HTML. You would have to create your own “next” and “previous” buttons and make sure the links are accurate, but other than that, this method is not as difficult as you might think. It is usually easiest to start with the content in the outline panel, and then add in images as well as visual styles.
You can also create an HTML outline in addition to the PowerPoint file. This would allow users to review the structure of your presentation in a browser without having to open the main presentation. To create an HTML version, select and copy the contents of the Outline panel, paste in into an HTML editor such as Dreamweaver, and clean up the content. You may also wish to add additional information to the outline, such as relevant images (with appropriate alternative text).