Resources

• 1: Technical Specification for Thorium Reader Desktop
• 2: Minimum system requirements
• 3: Keyboard shortcuts
• 4: Supported publication formats
• 5: Glossary
• 6: Frequently asked questions
• 7: Stuck?

1 - Technical Specification for Thorium Reader Desktop

Last updated 2025, October 6

About Thorium Reader Desktop Version: 3

App Overview

Purpose: Thorium is a digital book reader, it is also a library where you can store your books and access to online catalogs.

Target Audience: General public with a particular attention for heavy readers, library-goers, and students.

Supported Operating Systems:

• macOS (Big Sur, 11 and up)
• Windows (Windows 10 and up)
• Linux:
  • Ubuntu 18.04 and newer
  • Fedora 32 and newer
  • Debian 10 and newer

Hardware & Software Requirements:

• Both ARM 64 and AMD 64 architectures are supported via different installers.
• No additional software is needed to run Thorium Reader Desktop.

Major and minor versions: Thorium releases minor versions every 3 to 4 months; those are numbered with a dot and numbers after the main version number (e.g., 3.1.1). Those versions usually include bug fixes and enhanced features, but no breaking changes. This technical specification page addresses the main version and associated minor revisions. If a minor version introduces a notable difference, it will be clearly indicated in the relevant section.

Download, Installation, & Registration

Download

Thorium Reader Desktop is available on the Windows store and can also be installed directly from the installer files available from the Thorium website. A standalone (with no need to be installed) AppImage is also available for Linux, once this one downloaded, it is necessary to change permissions to make it executable as a program, then double-click on the Icon to launch the app.

Installation

• On Windows:
  • Select the download link corresponding to your Windows architecture (ARM 64 or AMD 64), this information is available from your system information panel.
  • Download the Thorium.Setup.3.x.x.exe file to your Windows device.
  • Open the Explorer and navigate to Downloads.
  • Double-click the downloaded *.exe file. Double-click the downloaded installer file and complete the installation process. Managed devices may require admin authorization to install.
• On MacOS:
  • Select the download link corresponding to your Mac architecture (Recent M1, M2, M3, M4 or Intel for Mac produced before fourth quarter of 2021), this information is available from your system information panel.
  • Download the Thorium.Setup.3.x.x.dmg file to your macOS device.
  • Open the Finder and navigate to Downloads.
  • Double-click the downloaded *.dmg file.
  • Now drag and drop the application icon to the Applications folder to install the application.
  • Close the window and press the eject button in Finder to dismount the image.
• On Linux:
  • Select the download link corresponding to your computer architecture (ARM 64 or AMD 64), this information is available from your system information panel.
  • Download the Thorium.Setup.3.x.x.deb file to your Windows device.
  • Open the Explorer and navigate to Downloads.
  • Double-click the downloaded *.exe file.Double-click the downloaded installer file and complete the installation process. Managed devices may require admin authorization to install.

Accounts & passphrases

• No account nor registration are necessary to use Thorium Reader Desktop.
• An account is necessary to access catalogs loaded into Thorium. In that case, the catalog provider is responsible for any related question, support or reclamation.
• A passphrase can be necessary to read protected ebooks. This passphrase is stored by the application after being entered once, and is therefore requested once only. The provider of the protected ebook is responsible for any related question, support or reclamation.

Supported publication formats

• EPUB (Electronic PUBlication), version 2 and 3 including Reflowable, Fixed-Layout and MediaOverlay variants.
• Web Publications both in their W3C and Readium flavors.
• DAISY, version 2.02 and 3, both in their text only, audio only, and syncronised text and audio flavors.
• PDF without support for forms nor annotations.
• Audiobooks standardized as per W3C packaged (LPF) audiobook format.
• Divina, an experimental format for comics, manga, webtoons and other styles of digital works based on sequences of images.

App features

• Load & Read ebooks: Thorium Reader Desktop allows you to load an ebook from your computer and read it in a dedicated windows.
• Organise ebooks: ebooks can be sorted, tagged, exported, deleted and lending can be managed from the Library window.
• Bookmark: Users can add, comment, tag, modify, sort, access, export and import bookmarks.
• Annotate: Users can add, personalize (with color and stroke), comment, tag, modify, sort, access, export and import annotations.
• Filter: Users can filter ebooks with a range of options, including free text (like search).
• Search: Users can search inside an ebook, list and navigate between search results.
• Add & Browse catalogs: Users can add catalogs in the OPDS format and browse them depending on the options provided by the catalog provider.
• Lend & acquire ebooks: Users can download ebooks from catalogs for a timeless access or under a time period depending on the catalog provider terms of lending or acquisition.
• Personalize: Users can personalize the reading experience according to the formats capacities.
• Accessibility: Users can use assistive technology to access and use Thorium Reader Desktop.
• User guide: Users can download, read online or load as catalog a complete user guide as ebook.
• Offline support: Thorium Reader Desktop can be used offline, however, online catalogs can not be accessed offline.

Security Information

Security Reports: security vulnerabilities must be reported privately to maintainers through the dedicated report a vulnerability page. A GitHub account is necessary. Alternatively, vulnerability reports can be sent by email at: contact@edrlab.org.

Data protection: Thorium Reader Desktop collects no personal data

Permissions: : Thorium Reader Desktop requires device access to the following:

• File system access - Required for downloading digital content (e.g. books) and storing annotations.
• Network access - Necessary for connecting third party catalogs and downloading digital content from those.

Network Communications: Thorium Reader Desktop works entirely offline by default. If network access is available, it uses only HTTP and HTTPS protocols, typically over ports 80 and 443, for these specific functions:

• HTTP POST https://telemetry.edrlab.org/ — Sends anonymized telemetry data (no personal information).
• HTTP GET https://raw.githubusercontent.com/edrlab/thorium-reader/master/latest.json — Checks if a new version of Thorium Reader is available.

When users add third-party catalogs (such as OPDS feeds), Thorium Reader may connect using HTTP or HTTPS with GET, POST, or PUT requests. These catalogs may use ports other than 80 and 443, depending on their configuration.

Thorium Reader Desktop does not use SSH, direct TCP connections, or WebSockets for any communication.

Troubleshooting

• User guide: is available in English, French and Spanish, as an ebook to Download or read online. The complete user guide catalog can be added to Thorium Reader. as EPUB, different translations are available through the Thorium documentation catalog. You can Add Documentation catalog to Thorium (OPDS link) or browse English documentation inline within the Readium web reader.
• Support: the webpage contains support information in English, French and Spanish. That includes Frequently asked questions
• Known/Common issues: are available publicly from our Issue tracker
• Error Reports: errors and problems should preferably be reported via our support tracking tool (necessitate a free GitHub account) or contact form. To reproduce and find a solution, we need to know Operating system and Thorium version (indicated at the bottom of the library under the title About Thorium).

Version

Current Version: 3

Version File Sizes:

• Windows AMD .exe: 102 MB
• Windows ARM .exe: 104 MB
• MacOS AMD .dmg: 129 MB
• MacOS ARM .dmg: 129 MB
• Linux AMD .deb: 89.6 MB
• Linux ARM .deb: 84.8 MB
• Linux AMD .app: 135 MB
• Linux ARM .app: 135 MB

Release Notes: Full release note are available from the code repository release page

Legal Information

EDRLab is the owner of the Application, including all copyrights, trademarks, trade names, logos, patents, trade secrets and other intellectual property rights relating thereto. EDRLab may license third parties for the use or operation of the Application.

Complete and up to date Terms of use are available from the Thorium Reader website. A short list is provided here for quick reference:

• We reserve the right to withdraw or modify the Application and any service we provide on it.
• We may change the Terms of Use from time to time.
• the user does not have and will acquire no rights in the Application, other than the right to use it under the Terms of Use.
• You may use the Application only for lawful purposes.
• In the event that you have authorized a minor to use the Application and its Content, you acknowledge that you are responsible for.
• The Application may import Content that is inappropriate for a minor.
• Contents imported in the Application can be protected by copyright or other intellectual property rights. You are responsible for ensuring that your use of the Contents, as well as of all the elements that compose them, does not violate any intellectual property right or any other right.
• By using the Application, you accept the terms of the privacy policy relative to the Application.
• Links to Other Sites or Resources in the Application links to third-party services or resources not operated by EDRLab, including Library data feeds. EDRLab has no control over such third-party sites or resources and is not responsible for their availability, security, Content or resources. The inclusion of such links does not imply an endorsement or a recommendation by EDRLab of the third-party service or resource in question. EDRLab is not responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with your use of or reliance on any Content, information, products, goods or services available on or through any third party service.

Applicable Laws and Jurisdiction These Terms of Use and any dispute arising out of or relating to these Terms of Use shall be governed by the laws in force in France, without reference to its conflict of law rules. Any action, suit or proceeding arising out of these Terms of Use (whether for breach of contract, wrongful conduct or otherwise) shall be brought exclusively in France, as the case may be, located in Paris, and you agree to submit to the jurisdiction of such courts for any action, suit or proceeding arising out of these Terms of Use.

Contact Us All questions, comments or requests regarding these terms of use should be sent to EDRLab at: contact@edrlab.org.

2 - Minimum system requirements

Platform support is provided by Electron as defined in Electron github repo Readme

Each Electron release provides binaries for macOS, Windows, and Linux.

• macOS (Big Sur and up): Electron provides 64-bit Intel and Apple Silicon / ARM binaries for macOS.
• Windows (Windows 10 and up): Electron provides ia32 (x86), x64 (amd64), and arm64 binaries for Windows. Windows on ARM support was added in Electron 5.0.8. Support for Windows 7, 8 and 8.1 was removed in Electron 23, in line with Chromium’s Windows deprecation policy.
• Linux: The prebuilt binaries of Electron are built on Ubuntu 20.04. They have also been verified to work on:
  • Ubuntu 18.04 and newer
  • Fedora 32 and newer
  • Debian 10 and newer

Thorium 3.0 has memories issues under Linux, as documented in Issue 2519

3 - Keyboard shortcuts

Keyboard shortcuts are available from the application settings panel third tab. It help you check and manipulate keyboard driven actions within the application. Figure out the three dots menu aside of the Panel title with extra actions (Reset, Edit and Load). The Edit one opens system folder application to the localisation of the stored user setting .json file, allowing you to edit it outside of the application (at your own risks), save it for future uses or share it within your devices or with who you want.

The following list is showing the default keyboard shortcut settings.

Create annotation (`AnnotationsCreate`) Alt + Ctrl + Shift + KeyA

When a text is selected, it will be marked as annotation and the annotation dialog box will open to allow additional text and select of color and stroke.

Quick create annotation (`AnnotationsCreateQuick`) Alt + Ctrl + Shift + KeyQ

When a text is selected, it will be marked as annotation without opening the annotation dialog box

Toggle annotation marks in the margin or in the text (`AnnotationsToggleMargin`) Alt + Ctrl + Shift + KeyZ

Changes the Annotations marks from the text to the margin or reverse.

Next audio (`AudioNext`) Ctrl + Digit3

in reader window, calls the "next" command for audio (TTS or EPUB3 Media Overlays readaloud, or "forward" for audiobooks)

Next audio Alternative (`AudioNextAlt`) Alt + Ctrl + Shift + Digit3

in reader window, calls the "next" command for audio (TTS or EPUB3 Media Overlays readaloud, or "forward" for audiobooks)

Play or pause audio (`AudioPlayPause`) Ctrl + Digit2

in reader window, calls the "play" or "pause" toggle commands for audio (TTS or EPUB3 Media Overlays readaloud)

Previous audio (`AudioPrevious`) Ctrl + Digit1

in reader window, calls the "previous" command for audio (TTS or EPUB3 Media Overlays readaloud, or "rewind" for audiobooks)

Alternative previous audio (`AudioPreviousAlt`) Alt + Ctrl + Shift + Digit1

in reader window, calls the "previous" command for audio (TTS or EPUB3 Media Overlays readaloud, or "rewind" for audiobooks). Alternative shortcut key.

Stop audio (`AudioStop`) Ctrl + Digit4

in reader window, calls the "stop" command for audio (TTS or EPUB3 Media Overlays readaloud, or "pause" for audiobooks)

Close the book (`CloseReader`) Ctrl + KeyW

in reader window, closes the window and returns to the library view.

Fixed Layout Zoom In (`FXLZoomIn`) Ctrl + Digit9

Zoom in a fixed layout page

Fixed Layout Zoom out (`FXLZoomOut`) Ctrl + Digit8

Zoom out a fixed layout page

Fixed Layout Zoom (`FXLZoomReset`) Ctrl + Digit0

Reset to 100% zoom on a fixed layout page

Main content(`FocusMain`) Ctrl + F10

In reader and library windows, moves the keyboard focus to the "main" area landmark. in the reader view, the keyboard focus moves one step further into the frame that displays publication content (screen readers automatically read the currently-focussed HTML element inside the displayed document)

Main content deep (`FocusMainDeep`) Shift + Ctrl + F10

Just like "Main content" / FocusMainDeep in the reader view (see above), but the keyboard focus is forced deeper into the frame that displays publication content (this can help in cases where screen readers do not automatically read the currently-focussed HTML element inside the displayed document)

Go to page (`FocusReaderGotoPage`) Ctrl + Shift + KeyP

in reader window, moves the keyboard focus to the "goto page" section in the navigation panel

Navigation (`FocusReaderNavigation`) Ctrl + KeyN

in reader window, moves the keyboard focus to the navigation panel (table of contents, bookmarks, etc.)

Table Of Content (`FocusReaderNavigationTOC`) Ctrl + Shift + KeyN

in reader window, moves the keyboard focus to the navigation panel, but more specifically into the table of contents, and if possible at the detected heading / closest to the reading location.

Reader settings (`FocusReaderSettings`) Ctrl + KeyS

in reader window, moves the keyboard focus to the settings panel (user preferences for displaying publication content)

Search (`FocusSearch`) Ctrl + KeyF

Available from the library and the reading winfos. In library window, moves the keyboard focus to the search text input of local bookshelf or OPDS feed. In reader window, moves the keyboard focus to the publication-wide search text input.

Toolbar (`FocusToolbar`) Ctrl + KeyT

in reader and library windows, moves the keyboard focus to the top horizontal toolbar, immediately before the "skip" link (which itself moves focus to the "main" area landmark)

Next chapter (`NavigateNextChapter`) Alt + Ctrl + Shift + ArrowRight

in reader window, move to previous or next "chapter" (spine item in the reading order of the publication). Note that the keyboard focus is automatically moved to the "main" area landmark, which is immediately before the frame that displays publication content (just like when following / activating a link in the table of contents).

Next chapter (`NavigateNextChapterAlt`) Ctrl + PageDown

in reader window, move to previous or next "chapter" (spine item in the reading order of the publication). Note that the keyboard focus is automatically moved to the "main" area landmark, which is immediately before the frame that displays publication content (just like when following / activating a link in the table of contents).

Next History (`NavigateNextHistory`) Ctrl + Shift + Backspace

in reader window, go back or forward in the navigation history: Beginning or End of the publication

Next library page (`NavigateNextLibraryPage`) Ctrl + Shift + ArrowRight

In the library view, display the next set of books

Next library page alternative(`NavigateNextLibraryPageAlt`) Ctrl + Shift + Period

In the library view, display the next set of books (alternative keyboard shortcut)

Next Catalogue page (`NavigateNextOPDSPage`) Ctrl + Shift + ArrowRight

in library window for Catalogues (OPD) feeds, activates the next pagination links

Next Catalogue page (`NavigateNextOPDSPageAlt`) Ctrl + Shift + Period

in library window for Catalogues (OPD) feeds, activates the next pagination links (alternative keyboard shortcut)

Next page (`NavigateNextPage`) ArrowRight

in reader window, move to previous or next "page" (or scroll unit, if pagination is disabled)

Next page (`NavigateNextPageAlt`) Ctrl + Period

in reader window, move to previous or next "page" (or scroll unit, if pagination is disabled)

Previous chapter (`NavigatePreviousChapter`) Alt + Ctrl + Shift + ArrowLeft

in reader window, move to previous "chapter" (spine item in the reading order of the publication). Note that the keyboard focus is automatically moved to the "main" area landmark, which is immediately before the frame that displays publication content (just like when following / activating a link in the table of contents).

Previous chapter (`NavigatePreviousChapterAlt`) Ctrl + PageUp

in reader window, move to previous "chapter" (spine item in the reading order of the publication). Note that the keyboard focus is automatically moved to the "main" area landmark, which is immediately before the frame that displays publication content (just like when following / activating a link in the table of contents).

Previous History(`NavigatePreviousHistory`) Ctrl + Backspace

in reader window, go back or forward in the navigation history: Beginning or End of the publication

(`NavigatePreviousLibraryPage`) Ctrl + Shift + ArrowLeft

In the library view, display the previous set of books

(`NavigatePreviousLibraryPageAlt`) Ctrl + Shift + Comma

In the library view, display the previous set of books (alternative keyboard shortcut)

Previous Catalogue page (`NavigatePreviousOPDSPage`)

Ctrl + Shift + ArrowLeft

Previous Catalogue page (`NavigatePreviousOPDSPageAlt`)

in library window for Catalogues (OPD) feeds, activates the previous pagination links (alternative keyboard shortcut)

Ctrl + Shift + Comma

Previous page (`NavigatePreviousPage`) ArrowLeft

in reader window, move to previous or next "page" (or scroll unit, if pagination is disabled)

Previous page (`NavigatePreviousPageAlt`) Ctrl + Comma

in reader window, move to previous or next "page" (or scroll unit, if pagination is disabled)

Go to Begining of the book (`NavigateToBegin`) Ctrl + Home

in reader window, goes to the beginning of the publication

Go to end of the book (`NavigateToEnd`) Ctrl + End

in reader window, goes to the end of the publication

Book information panel (`OpenReaderInfo`) Ctrl + KeyI

in reader window, publication info popup modal dialog (may be used in future Thorium version for similar feature in library window)

where am I (quick notification supported by Screen readers) (`SpeakReaderInfoWhereAmI`) Ctrl + Shift + KeyK

in reader window, this is the "where am I" feature, just as above, but only spoken via screen reader TTS thanks to an ARIA live region with assertive speech which interrupts the current narration.

where am I (`OpenReaderInfoWhereAmI`) Ctrl + Shift + KeyI

in reader window, publication info popup modal dialog with direct keyboard focus on section that displays the headings hierarchy trail and other contextual information for the current reading location, such as nearest preceding page break, as well as document index in the reading order (this is the "where am I" feature).

Next search result (`SearchNext`) F3

in reader window, when the publication-wide search text input is open, finds the previous / next match

SearchNextAlt Ctrl + KeyG

same as above (alternative keyboard shortcut)

previous search result (`SearchPrevious`) Shift + F3

in reader window, when the publication-wide search text input is open, finds the previous / next match

(`SearchPreviousAlt`) Ctrl + Shift + KeyG

same as above (alternative keyboard shortcut)

Bookmarks (`ToggleBookmark`) Ctrl + KeyB

in reader window, toggle bookmark (a notification is produced so that screen readers announce the change)

Fullscreen (`ToggleReaderFullscreen`) Ctrl + F11

In reader window, toggle fullscreen. Note that this is different from the Zen mode. Keyboard shortcut is the only way to go full screen.

4 - Supported publication formats

EPUB

(Electronic PUBlication) is an open file format for electronic publications. EPUB is a native semantic format allowing to use numerous standardised languages such as HTML, ARIA, MATHML, SVG and others. The actual version 3 is known to provide the best up to date reading experience. Obsolete EPUB2 files are also readable in Thorium.

DAISY

Usually produced and distributed by specialized libraries or NGOs, the DAISY format offers a significantly enhanced reading experience for ebooks that are not available in EPUB3. Thorium supports reading DAISY 3 and 2.02, both in their text only, audio only, and syncronised text and audio.

PDF

despite a well-known lack of flexibility (no reflow option) and accessibility, many ebooks are still available in PDF only, especially in public libraries.

Audiobooks

a standardized format for audiobooks has been designed by the W3C Publishing Working Group in 2020, and EDRLab was part of this WG. Thorium is supporting the packaged (LPF) audiobook format, which will soon be widely used by booksellers, or so we hope.

Visual narratives

EDRLab has designed a standard format for comics, manga, webtoons and other styles of digital works based on sequances of images. Divina is the name of this format. This is still an experimental format, and we hope that publishers will size it in 2021+.

5 - Glossary

Book information panel (Book Details)

Gives information about the digital book. This information is extracted from the file's metadata, its quality and quantity depends on the the attention paid during the production of the file by the publisher.

Adapted books

These are digital books produced by associations and made available to people with disabilities for reading. Worldwild, this system is governed by The Marrakech Treaty .

OPDS

Open Publication Distribution System

6 - Frequently asked questions

How can I enjoy Thorium in Fullscreen?

Ctrl + F11 in a reader window, will toggle this window fullscreen. Note that this is different from the Zen mode available from the top right pictogram. Keyboard shortcut is the only way to go full screen.

Why can't I open an ebook without it being save in the Thorium Reader library?

Thorium, like several other ebook readers and reading systems stores imported publications in its own filesystem space, as this provides a guarantee that per-publication state and external metadata (e.g. bookmarks, settings, annotations, DRM status, etc.) can be reliably attached.

Why is there no read aloud nor annotations for PDFs?

EDRLab prioritises its work on offering a great experience to EPUB users. In Thorium Reader, advanced features like TTS and annotations are consequently available for EPUB first, and we expect that other app developers will get the best from PDF files. It does not mean that advanced features will never be available on PDF in Thorium, simply that our limited budget is used for what we consider best for ebook readers.

I accidentally rotated my PDF pages, how can't get it back?

The shortcuts for rotating PDF pages are:

• Rotate the document clockwise: r
• Rotate the document counterclockwise: shift + r

I can't select the adequate voice for read aloud function (TTS)

Thorium uses the voices from the computer's operating system, in combination with the language information provided by the book.

• If you are using windows you can follow Microsoft’s guide Download the language pack for voice.
• If you are using Mac OSX the guide Change the voice that the Mac uses to pronounce text.

Once the required voice is installed, Thorium will choose the voice corresponding to the language of the book.

It may happen that the book has the wrong language. In this case, Thorium allows you to change the voice to one that is present in the system via the Voice menu

How can I transfer the entire book collection from one machine to another?

Having a UI for exporting the whole catalog is not a priority currently.

The publications are stored in a well-known directory.

• on Windows10: C:\Users\ user name \AppData\Roaming\EDRLab.ThoriumReader\publications\
• on MacOS: /Users/ user name /Library/Application Support/EDRLab.ThoriumReader/
• on Debian: /home/ user name /.config/EDRLab.ThoriumReader/publications-dev/

In case of a migration from one computer to another or similar usecases, you can copy all ebook files in this repository and open them in the new installation of Thorium.

7 - Stuck?

If you do not find the answer to your problem on this site, you can tell us your problem via our support tracking tool or contact form.

Here is the information we need:

• Operating system and it version
• Thorium version (it is indicated at the bottom of the library under the title About Thorium)