Guides

What Is an EPUB File? A Simple Guide for Desktop Readers

You’ve downloaded a “.epub” file and your computer doesn’t know what to do with it. Is it a book? A document? Something else entirely? In this guide, we’ll explain what an EPUB file is, why it’s so common for ebooks, and how to open and read EPUBs comfortably on your computer using Wizread. If you’re also wondering how it compares to other formats, you can later dive into our EPUB vs PDF guide for desktop reading or our EPUB vs MOBI vs AZW3 comparison .

What is an EPUB file, in plain language?

An EPUB file is a digital book format. Think of it as a modern, flexible version of a book that can live on your computer instead of on a shelf.

It’s designed specifically for reading text (novels, non-fiction, long articles).
The text is reflowable, which means it can adapt to different screen sizes and layouts.
It usually contains chapters, a table of contents, images and metadata (title, author, etc.).

On your computer, an EPUB is just a file with the .epub extension. To read it, you need an app that understands ebooks—like Wizread—rather than a generic document viewer. If you’d like a step-by-step walkthrough for actually opening them on each OS, you can continue with our “how to open EPUB files on Windows, macOS and Linux” guide after this one.

EPUB vs “just a PDF”

EPUB and PDF are the two formats you’ll see most often when dealing with ebooks and documents. The big idea:

Format	How it behaves	Best for
EPUB	Text reflows to fit your window and settings, like an ebook.	Book-like reading on desktop and other devices.
PDF	Layout is fixed, like a printed page.	Documents where exact layout and page breaks matter.

Wizread supports both EPUB and PDF, so you can keep novels, essays and documents together in one library on your computer and open them with the same flow. For a deeper, practical comparison of the two formats specifically for desktop reading, see EPUB vs PDF: Which format is better for reading on your computer? , and if you read a lot of PDFs you can also check how to read PDF files like ebooks on your desktop .

What’s actually inside an EPUB file?

You don’t need to look inside an EPUB to use it—but understanding the basics helps it feel less mysterious.

Under the hood, an EPUB is usually:

A container (often a ZIP archive) that holds everything together.
Chapters written in HTML/XHTML (like simple web pages).
CSS styles that control fonts, spacing and basic layout.
Embedded images for covers, illustrations or figures.
Metadata describing the book (title, author, language, etc.).

A reading app like Wizread takes all of that structure and turns it into a clean, readable view for you, so you don’t have to think about the internal pieces at all.

Where do EPUB files usually come from?

If you’ve ended up with an EPUB, it probably came from one of these places:

Publishers and authors offering ebook downloads.
Online libraries and archives.
Documentation sites or technical book providers.
Conversion tools that turned another format into EPUB.

Once the file is on your computer, it’s just another part of your library—you can move it into your main Books/ folder and import it into Wizread whenever you’re ready to read it. If you’re building a bigger collection over time, our guide on organizing your ebook library on Windows, macOS and Linux shows a simple folder structure that works well with Wizread. And if you’re concerned about safety when downloading new books, you can also read Are EPUB and PDF files safe? for practical tips.

How to open an EPUB file on your computer with Wizread

On Windows, macOS and Linux, an EPUB won’t open by default unless you tell your system what to use. With Wizread, the process is always the same:

Step 1 – Open Wizread

Launch Wizread on Windows, macOS or Linux.
Make sure the main library view is visible.

Step 2 – Import your EPUB

You can add the book to Wizread using either of these actions:

Drag & drop
Open the folder where your .epub file is located, then drag it into the Wizread window.
Use the “Import book” icon
Click the Import book icon in the top navigation bar and select the EPUB from the system file picker.

Once imported, the EPUB appears in your Wizread library alongside your other books and documents. For a more detailed, OS-specific walkthrough, you can also read how to open EPUB files on Windows, macOS and Linux .

Step 3 – Click “Read”

Find the newly imported EPUB in your library.
Click the Read action for that title.
Wizread opens the reading view, focusing entirely on the book’s content.

From here, you can read and take notes in the same place, using the same flow for all your EPUB books. If you want to make those reading sessions more comfortable on your eyes, you can also follow our guide to making EPUB and PDF more comfortable on desktop .

Why EPUB is a good choice for desktop reading

If you have a choice of formats for a book you’ll read on your computer, EPUB is often the most comfortable:

Text adapts to your window, making it easier to read on different monitors.
Books behave consistently across platforms—Windows, macOS and Linux.
EPUB files tend to be lightweight, especially for text-heavy content, so your library doesn’t explode in size.

In Wizread, EPUB files fit naturally into the idea of a reading session: you import them once, then open them from your library whenever you’re ready to continue. If you also have other formats like MOBI or AZW3 and want to bring them into this setup, our guide on converting Kindle books (AZW3/MOBI) to EPUB or PDF explains how to normalize everything around EPUB/PDF for desktop reading.

Common questions about EPUB files

“Can I just rename a PDF to .epub?”

No. Changing the file extension doesn’t convert the format—it just breaks the file. If you want to turn a PDF into an EPUB, you need a proper conversion tool. Wizread can read both EPUB and PDF directly, so in many cases you don’t need to convert at all. For deciding when to prefer one format over the other on desktop, see our EPUB vs PDF comparison .

“Why won’t my EPUB open in some apps?”

Some EPUBs are DRM-protected or created specifically for certain stores or apps. Those files may only open in the official ecosystem they were meant for. For DRM-free EPUBs, using a dedicated reader like Wizread on desktop is usually straightforward. If a particular file keeps failing, our troubleshooting guide “EPUB won’t open – common errors and fixes” can help you narrow down what’s wrong.

“Is EPUB safe?”

EPUB is just a file format; safety mostly depends on where you download it from. As with any file, stick to trusted sites and sources, let your system’s security tools do their job, and avoid opening random files from spam emails or suspicious links. For a deeper look at safety habits around EPUB and PDF before importing them into Wizread, see Are EPUB and PDF files safe? .

Recap: EPUB as part of your desktop reading setup

You don’t need to be a file-format expert to use EPUB. All you really need to remember is:

EPUB is a digital book format, great for long-form reading on your computer.
It’s reflowable, so text adapts to your screen instead of being “stuck” to a page size.
Wizread supports both EPUB and PDF, so you can import and read them with one flow.
To read an EPUB in Wizread: open the app, import the file (drag & drop or Import book), then click Read from your library.

Once you get used to thinking of .epub as “this is a book for Wizread”, it becomes a natural part of how you collect, organize and read on your desktop. From there, you can refine the rest of your setup with a simple cross-platform ebook organization system and tips for making EPUB and PDF more comfortable on desktop so reading on your computer actually feels good.