Not all file types used on desktop and laptop computers are well supported by iOS and Android. The formats below should be readily openable on iOS and Android devices, either natively or with a variety of common apps. Also, while these apps may act as viewers, not all allow editing. When distributing files to your students, consider what they can easily use on their phones or tablets. If the file format is uncommon, recommend apps for both Android and iOS that can open it.
Unsupported or Poorly Supported Common Formats
The following types of files should be avoided:
- Flash. No iOS device will play Flash natively and Flash support was discontinued with Android 4.1. Though some Flash files may be played through special browsers that convert the Flash to another video standard, this will not work with all Flash files. Use HTML 5 for interactive content, or one of the video formats listed in the next section.
- Java. No iOS supports Java and Android support is limited and variable depending on the Android Version.
- RTF. While this format is viewable on iOS devices, editing RTF files is not. Android apps that open RTFs may not be able to open all of them correctly and cannot edit them.
- CSV. While CSV is considered a universal format for spreadsheets, not all mobile spreadsheet apps support it. Those that do may have difficulties with specific files.
Well-supported File Formats
We would recommend using these formats to maintain compatibility with mobile devices:
MS Office files. Both the old (.doc, .xls, and .ppt) and the new (.docx, .xlsx, and .pptx) Word, Excel, and PowerPoint formats work well with iOS and Android devices.
- At one time, we suggested that instructors use RTF instead of DOC due to virus concerns. This is much less of a concern now, and, given the lack of good RTF support on mobiles, we suggest using the native Word formats.
- Only a subset of Excel functions are supported by any given mobile spreadsheet app. Most common functions should work normally.
- As happens when moving PowerPoint files between Windows and Mac, you may see changes to fonts, minor formatting, and transitions and animations when moving between desktop and mobile applications.
- PDF. PDF files are an excellent choice for documents that students will not have to edit. Be aware, however, that, unlike Word, plain text, or EPUB, PDFs will not usually reflow, i.e., the line breaks are preserved so that the lines will not wrap to accommodate a small screen. For this reason, PDF files are not as useful on phones as they are on tablets. If this is a consideration, an Office format or EPUB is preferable.
- EPUB. This is the standard format for most ebooks (other than for Kindle). Because it will reflow lines and so adapt to any sized screen, it is in many ways preferable to PDF. Some word processors, such as Pages, can export directly to EPUB, while free programs like Calibre and Sigil can convert documents to EPUB. Apple's iBook Author exports a version of EPUB that only works correctly with the company's iBooks app on iPad.
- Graphics. Stick with the old standards for graphic formats. GIF, JPEG (JPG), and PNG are pretty much universal standards. Avoid using TIFF as Android does not provide native support. SVG is also not well supported.
- Audio. The most common are MP3 and MP4 (also called M4A) and WAV. We would recommend MP3 and MP4 files as they are smaller, compressed files that will take less time to download and take up less storage.
- Video. To maintain compatibility between Android and iOS, we recommend using MP4 video (MP4 or M4V).