A file format that provides an electronic image of text or text and graphics that looks like a printed document and can be viewed, printed, and electronically transmitted.


Because PDFs are a standardized format, there are a considerable number of programs and apps out there that can open them. Web browsers, Acrobat Reader, numerous third-party apps, and even a word processor will read pdf files.  If you don’t have another app that can read PDFs, chances are that your browser is already the default app and you can just double-click the file to open it.


Adobe’s Acrobat Reader is the official tool for reading PDFs. It’s free, and it’s available for Windows, macOS, iOS, and Android.



Because of their widespread use, more hardware eReaders support EPUB files than any other eBook file format. You can open an EPUB file whether you’re using a Kobo, Barnes & Noble Nook, or even on your desktop using one of the many free programs, such as Calibre or Stanza Desktop. The notable exception here is Kindle. You cannot read an EPUB file directly on a Kindle, but there are ways to convert one to something the Kindle can use.

iPhone and Android devices come preloaded with their own applications to open EPUB files —iBooks and Google Play. If you’re trying to open one on your desktop, you’ll probably want a third-party application.  If you use Windows 10, Microsoft Edge can display EPUB files natively. If Edge isn’t already set up as the default program to handle EPUB files, right-click on the file, point to the “Open With” menu, and then click the “Microsoft Edge” option.

Unless you’re using Kindle, which uses a proprietary file format, your eReader probably already supports EPUB, and all you have to do is open the file on your eReader or smartphone device. But you can use an EPUB file on your Kindle; you just have to convert it first.  For this, we again recommend Calibre. It not only lets you open and view eBooks, but it also has a powerful tool that can convert your file into one of 16 different formats, including the MOBI format that your Kindle can open.

MOBI (Kindle)

A MOBI file is specifically designed for mobile—or eReader—devices. The format is very lightweight in size and supports bookmarks, notes, corrections, and JavaScript.  The current Kindle formats (AZW3, KF8, and KFX) are based on MOBI and is a proprietary format exclusively used on Kindle devices. And, in fact, you can still open files with the MOBI format directly on your Kindle—you just have to send them to your Kindle first.

Because MOBI is an eBook format, most free desktop eReader programs support opening and viewing them—like Calibre, FBReaderMobipocket Reader, or Mobi File Reader, to name just a few.  Just like any other file formats, you need specialized software to handle converting MOBI into a different format. If you simply try to change the extension, you could wind up with a corrupt and unusable file.  For this, we again recommend Calibre.

If you don’t want to download a third-party application to convert your files, there are a couple of really good online converters that allow converting into some of the more popular formats, like ePUB, PDF, FB2, and LRF. This is probably one of the fastest ways, as you don’t have to download any software and wait for it to install.

Some free online file conversion sites include: DocsPalConvertioConvertFiles, and Zamzar.


MP3 (MPEG-1 Audio Layer-3) is a standard technology and format for compressing a sound sequence into a very small file (about one-twelfth the size of the original file) while preserving the original level of sound quality when it is played. MP3 provides near CD quality audio depending on its bitrate, 320 being the highest.



A ZIP file is an archive that contains one or more files compressed or "zipped" using Zip compression. It stores files separately from each other allowing the files to be compressed using different methods and extracted without compressing or decompressing the entire archive.  In order to work with zipped files, they must be unzipped or extracted first.  Most devices have built-in support for this function.


An ISO file (often called an ISO image), is an archive file that contains an identical copy (or image) of data found on an optical disc, like a CD or DVD. They are often used for backing up optical discs, or for distributing large file sets that are intended to burned to an optical disc.


Windows 8, 8.1, and 10 all let you mount an ISO image without any third-party software. Just select the image in File Explorer, and then head to Manage > Mount.  Windows 7, 8, and 10 have a feature for burning an ISO image to disc built right in. All you have to is insert a writable optical disc, right-click the ISO image, and then select the “Burn Disk Image” command.  If you don’t want to mount an ISO or burn it disc, but still need to access to the files inside, you can extract the contents to your PC. For this, you’ll need a third-party app like WinRAR or 7-Zip. We like 7-Zip around here because it’s free, open-source, and plenty powerful.


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