Thorium Reader is a cross-platform and open source eBook reader application

May 24, 2021
Updated • Jun 15, 2021
Windows software

Do you read eBooks on your computer? If you're bored with your current eBook reader program and want a new one, you maybe interested in Thorium Reader.

Thorium Reader is a cross-platform and open source eBook reader application

The open source program is user-friendly, and supports a variety of formats; EPUB, EPUB3, PDF, ZIP, LPF, Audiobook, Webpub, LCPA, LCPDF, LCPL, Divina, Daisy and OPF.

Thorium Reader - My Books

Thorium Reader's interface couldn't be simpler, it has two tabs. The My Books tab, is your eBook library. To add your books from the start page of the app, you can either use the + button to browse, or drag and drop an eBook onto the interface.

Thorium Reader - List view

Once you have imported the books to the program's library, they are listed on the home page. Only the recently added books are listed here, switch to the All Books section to browse your entire library. Thorium Reader displays the title, author name, and cover of the books. Hit the three-dot button to delete or export a book, the about section displays the eBook's description, cover, publisher info. It also allows you to add tags.

Thorium Reader ebook interface

Use the Search bar to find a book. Toggle the view between grid (thumbnail) view and list view using the buttons next to the search bar. Switch to the Catalogs tab in Thorium Reader. You may add an OPDS feed (Open Publication Distribution System) from online services, or your own server, and browse the catalog. I tried it with some Atom feeds, and it works pretty well.

Thorium Reader - Sepia theme

Click on a book's cover to start reading it. Thorium Reader has a toolbar at the top with some useful shortcuts. The back arrow button closes the current book and returns the focus to the bookshelf. To view both the book and the library at the same time, click the 3rd icon. The speaker icon toggles the text-to-speech mode, which uses the system's voice accessibility options (Microsoft David and Zira). The book icon lets you view the contents, chapters, and also the bookmarks that you added.

Use the arrow buttons/bar at the bottom or the right and left arrow keys to navigate between pages. The buttons toward the right edge of the toolbar are options you commonly find in most reader apps. The search icon is useful for finding content in the book page, that can come in handy if you want to jump to a specific section. Bookmark a page, and you can pick up where you left off.

Thorium Reader has three themes Neutral (Light), Sepia, and Night, which you can access from the aa menu > theme. Adjust the font size, type, page layout, alignment, columns, and the spacing settings for margin, word, letter, paragraph and line, from the aa menu. The last option on the toolbar toggles the full screen reading mode. The program supports many keyboard shortcuts, e.g. Ctrl + B toggles the bookmark, Ctrl + F11 jumps to full screen mode, etc. You can find the full list of hotkeys under the settings.

Thorium Reader OPDS feed catalog

Thorium Reader is available for Windows, macOS and Linux. The Electron app can be downloaded from the Microsoft Store and the GitHub Repo, though a portable version is not available.

Looking for a comic book reader? You may want to check out YACReader.

software image
Author Rating
4.5 based on 5 votes
Software Name
Thorium Reader
Operating System
Windows, macOS, Linux
Software Category
Landing Page

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  1. Donald Stewart said on August 18, 2021 at 11:31 pm

    I used BookCreator to write an epub, and Thorium is great. But today I dropped in several PDF files that look great on BookCreator–the PDF opens fully, ready for download–but when I click that Adobe icon using Thorium, it takes me to the last page of the book, solid black.

  2. Raamil said on May 25, 2021 at 8:50 pm

    Sumatra PDF 3


    Icecream Ebook Reader 5 (epub, mobi, cbr & more)

    1. Karol said on May 27, 2021 at 12:16 am

      I use universal viewer for reading epub and mobi. I just want a real ebook reader without a library:

  3. shscs911 said on May 25, 2021 at 5:50 am

    When it comes to Windows, Freda Ebook Reader is hands down the best Ebook Reader. I was a long time Calibre user with custom CSS theme and keybindings, but the Calibre 3.0 update trashed my setup. I still use Calibre, but only as a personal library and ebook conversion tool. If you’re a Linux user, check out Foliate Ebook Reader. It’s miles ahead of any other Ebook readers, with tons of customization options, TTS and Dictionary integration.

    1. simnoo said on May 25, 2021 at 2:24 pm

      I tried Freda and didn’t like it. It also messed up the layout of several epubs, while other readers display them properly. Plus it has ads and needs to be installed through the MS Store.

      I think Calibre viewer is the best ebook reader on Windows, as long as you don’t mind its slow start.

  4. smaragdus said on May 24, 2021 at 9:56 pm

    gHacks has become a showroom for Electron/JavaScript/TypeScript junk thanks to Ashwin. What a shame! This site once used to offer valuable articles about valuable programs

    1. owl said on May 25, 2021 at 7:43 am

      > gHacks has become a showroom for Electron/JavaScript/TypeScript junk thanks to Ashwin. What a shame! This site once used to offer valuable articles about valuable programs

      Your lament is an outpouring of your feelings and a good indication of your values.
      Probably many of the skilled users “feel” that way too.

      However, “Ghacks” is Ghacks Tech News.
      GHacks is required to provide “information” to the beneficiaries (end users) of the “web” environment that has now become an integral part of our daily lives.
      In other words, the skills and values of end users are diverse. It is very important to provide useful information for beginners as well as information for high-end users.
      To a (skilled) user like you, the information may be useless and ridiculous.
      But to a beginner, information is useless, information that requires skill (For example, a graduate level topic is incomprehensible to the average person).
      And By having “Ghacks” deliver the news, the community (a place where people exchange skills and information about common goals and topics, even if they have different values and means) functions, and useful information is added (which becomes a source of knowledge for the beginner).

      We tend to think of ourselves as the standard, but we must not forget the existence of the silent majority.

      I am not interested in this article because I do not use the “E-book reader application” (I prefer the old style “reading books”). However, I do read through all the articles, not only this one, for the “sake of later learning”.
      I have always found Ashwin’s articles to be useful and “silent majority friendly”!

      1. owl said on May 25, 2021 at 7:56 am

        I used to use e-books in the past, but since I switched to a “digital detox lifestyle” at home, I try to avoid using “web” applications as much as possible and have stepped away from e-books.

  5. Darth Agnon said on May 24, 2021 at 7:18 pm

    DO NOT INSTALL Thorium

    It hijacks a lot of filetypes and sets itself as default on Windows ( I installed it and it hijacked Calibre’s .opf metadata files. It also cannot read Calibre libraries from custom locations, but creates a new one at %UserProfile% (Mine is saved in %UserProfile%\Documents)

    1. me said on May 25, 2021 at 5:29 pm

      Just uninstalled this crap because of this.

    2. DhulK said on May 25, 2021 at 8:11 am

      It did not do any of those things on my Windows 10 system. I had to set it manually as the default application for .epub, and .opf is still correctly associated with Calibre. .zip and .pdf are also associated with their respective apps as they had been before installing Thorium.

  6. DhulK said on May 24, 2021 at 12:38 pm

    Good find. I was looking for some kind of a replacement for Sumatra epub reading capabilities, as that app seems to be no longer in active development and a good number of my ebooks aren’t properly displayed. Calibre is beyond excellent for transferring stuff to my Kindle, but I find their built-in ebook viewer convoluted, ugly and quite slow on cold start after double-clicking a file in Explorer. Thorium seems to offer a nice ebook reading experience on my desktop monitor with decent performance.

  7. Anonymous said on May 24, 2021 at 12:30 pm

    No thanks. Its Electron. Stop being lazy devs. Why not QT for once?

    1. Darth Agnon said on May 24, 2021 at 6:59 pm

      Qt and Electron are sorta interchangeable, aren’t they?

      BlueStacks (the android emulator) recently did a major version bump (v4 to v5) and are advertising improved speed, less RAM usage, etc.

      Under the hood, the main change seems to be a switch from CEF/Electron to Qt (official documentation is rather sparse, amid their SEO spam), from examining the installed files.

      I’m testing, but so far, so good. They’re not lying about performance and RAM improvements, thanks to using Qt. Just need to wait for the Bluestacks rooting tools to catch up with v5, so it can be used without ads.

  8. beemeup5 said on May 24, 2021 at 10:43 am

    I’ve tried a lot of readers for Windows and so far Calibre’s own built-in reader is the best so far.

    Sigil is also really good for reading and editing at the same time.

  9. Paul(us) said on May 24, 2021 at 10:31 am

    Jim, Have you tried already Calibre?
    I am a satisfied user of many years of the program and I never found an easy to handle and also more advanced program?

    1. Jim said on May 24, 2021 at 5:13 pm

      Yes, and I use it for converting files. But for just reading/viewing/opening files it’s very slow and clunky.

      Sumatra is way faster, but it’s too limited in terms of functionality.

  10. Jim said on May 24, 2021 at 10:04 am

    It’s an Electron app, unfortunately. But there aren’t many ebook readers for Windows, so maybe it’s worth a try.

    1. beemeup5 said on May 24, 2021 at 11:06 pm

      I think this is one of the very few cases where Electron is a good choice. EPUB is basically a constrained spec of HTML and CSS with XML metadata so with Electron it’s a perfect match.

      EPUB3 has a clearly defined spec for fixed layout rendering, something that gave PDF the edge over EPUB for a long time, especially for textbooks and other academic journals which looked terrible on older EPUB.

      1. Jim said on May 25, 2021 at 9:42 am

        @beemup5: I dislike Electron apps, because they tend to “pollute” the system and install in weird locations and this one is no exception:
        They’re also a bit slower and use more resources.

      2. beemeup5 said on May 25, 2021 at 9:30 pm

        Sounds like it really needs a “portable” version.

      3. Mike said on May 25, 2021 at 5:35 pm

        I have to agree with Jim. I have installed Thorium on my personal laptop. I started to fiddle a little with it, then I got “weirded out” and tried to uninstall and then reinstall. The whole thing blew up and I haven’t been able to open an e-book in Thorium ever since. Even uninstalling it and then trying to delete all the remnants still doesn’t fix anything. I probably did a lot of horrible computing maneuvers in the whole process when I look back, but I have never been able to come out of it the same as I was before I installed it.

    2. Dumbledalf said on May 24, 2021 at 10:40 am

      There is always Calibre.

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