Is Calibre Safe to Download? Is There a Better Alternative?

Calibre is a free, open-source eBook management software. It has many different features, allowing you to manage, organize, edit, and even convert your ebooks into different formats.

But many users have concerns about the software. Some of these concerns are privacy-related (what information does Calibre collect?). Other concerns are about ensuring that it's safe to download. We'll tackle all these concerns as we answer whether the Calibre eBook software is safe.

In this article, you will learn:
  1. What Calibre is
  2. If Calibre is safe
  3. Formatting benefits and limitations for indie authors using Calibre

What is Calibre?

Before we dive into whether Calibre is safe, it's important to understand what the software does. Calibre gives you the power to manage your eBook collection. You can use it to convert one eBook format to another, edit eBook files, and view your ebooks by using it as an e-reader.

The virtual library management tools allow you to store and sort all your ebooks in one place, organizing and searching for them by metadata. You can also use Calibre to send ebooks to various e-readers, including emailing them to your Kindle device, Android device, and a number of other e-book reader devices.

Some indie authors use Calibre to format their eBooks. Since it's free, this can be tempting, especially for those just starting out or authors on a shoestring budget. With a bit of work, you can upload DOCX files and turn them into EPUB files using the software.

Is Calibre Safe?

Overall Calibre is safe to download and use — provided you download it from the Calibre website and take common-sense precautions, like using a secure network and some kind of anti-virus software. You can also rest assured that only a minimum of personal data is stored and never sold.

The makers of Calibre say that they don't store or sell their users' personal information. When you first download Calibre, it takes note of the version of the software you downloaded, giving it a randomly generated ID number that stays the same through updates. This number is used for usage reports and data, which are collected anytime a user opens Calibre.

How Many People Use Calibre?

A great way to determine the safety and efficacy of a tool is to see how many people use it and whether they're satisfied with it. Overall, Calibre has good ratings on the various platforms. It also has a lot of downloads.

At the time of this writing, Calibre has 2,911,392 active downloads. These aren't individual users, though. Some people have multiple downloads on different devices. Still, it's a good indication that the software is safe and well-liked.

Those who have reviewed the software on the various review sites generally have good things to say. Most sites that allow users to rate Calibre currently have the software sitting between 4 and 5 stars.

How Calibre Works

Calibre is available on Windows PC, Windows 64-bit, Linux, and Mac. (You can use an earlier version of Calibre if you're running Windows Vista.) Once you download the software, you can launch Calibre and use it to convert ebooks from one format to another.

Say you have a Kindle book in MOBI format, but you just got a new eBook reader that only recognizes EPUB files. With Calibre, you don't have to go out and buy the book again in EPUB format. Instead, you can simply upload your MOBI file to the software and convert it to EPUB.

There are a lot of supported formats to choose from for both input and output.

Some supported input formats include:

  • DOCX
  • PDF
  • EPUB
  • HTML
  • PDF
  • MOBI
  • LIT
  • AZW
  • ODT
  • TXT

Some supported output formats include:

  • EPUB
  • PDF
  • DOCX
  • MOBI
  • TXT
  • AZW3

The interface is pretty simple and format conversion is easy. Once you convert an ebook, both versions will be in your Calibre library so you can access them at any time.

Other Calibre Features

You can also use Calibre to access news websites, allowing you to download the day's news for you to read with the built-in eBook viewer or to send to your e-reader of choice.

You can also edit your eBook metadata to make it easier to find. This allows you to organize your book collection how you want.

There are also third-party plug-ins you can use, like Calibre companion, which you can use on your mobile device to manage your library and download books to read (through an e-reader app).

Converting Your Manuscript for Upload to Online Stores

If you're looking for a safe way to format your manuscript to a file format you can upload to online stores, Calibre is one option. However, there are some things to keep in mind before going ahead with this.

Format Before You Upload

While Calibre works for eBook conversion, it doesn't have the features that other tools have. For example, you can't choose from pre-made eBook templates and convert your file with a couple of clicks. If you want a certain style for your ebook, you'll need to change it manually before you upload it to Calibre.

So if you just upload a basic manuscript to Calibre and convert it to EPUB, it will work on any device that can read EPUB files, but it will still look like a basic manuscript. To get a great-looking ebook, you'll have to put in the work first to change your manuscript.

Valid EPUB Not Guaranteed

One big limitation of Calibre is its EPUB creation. If you're looking to upload an EPUB to a store for sale, there's no guarantee that your EPUB will read as valid. Not all stores have validity checkers, but those that do may give you problems. If your EPUB is not valid, it may not look right on some e-readers.

The way around this is to make sure you're formatting from a valid XHTML + CSS file from the beginning.

No Print Formatting

While it's possible to convert your manuscript to a PDF file, it won't be a print-ready file unless you first do the formatting in the manuscript. Manually formatting a print manuscript is one task that many authors struggle with. Thankfully, there are plenty of tools out there that do this automatically (like Atticus).

Formatting With Atticus

atticus logo

If you don't have the time or inclination to manually format your manuscript — and to deal with the troubleshooting that usually goes along with this — then check out Atticus.

You can choose from a wide variety of ready-made styles for easy formatting for both eBook and print. With just a few clicks, you'll have a great-looking book you're proud to upload to online stores. Plus, you won't have to worry about not having a valid EPUB.

atticus device previewer

Whether you're uploading to Amazon Kindle Direct Publishing only, or you're planning on uploading to as many stores as you can, Atticus can help. You can change styles, fonts, chapter headings, and print settings in just a few minutes. Plus, you can use the preview option to see how your book will look on various eBook readers and in print.

You can also write and edit in Atticus, making it easy to fix small mistakes or tweak things without having to upload your changed manuscript every time you want to format your book.

You can check out the Atticus book writing and formatting software here.


All in all, Calibre is a safe eBook library management tool and format converter. As long as you use common sense precautions and download the app from the official website, you shouldn't have any problems.

If you're looking to use it for converting your manuscript to a format you can upload to online bookstores, you're better off using a tool like Atticus. Calibre isn't expressly made for creating store-ready eBook formats, which means you could face some problems on the way — and you may not even end up with a usable EPUB file.Check out this article on formatting with Atticus to learn more.

Sell more books on Amazon

Free Download

Amazon Kindle Rankings E-Book

Learn how to rank your Kindle book #1 on Amazon with our collection of time-tested tips and tricks.