Sioyek review: a PDF reader for private study

Sioyek is a free open-source PDF viewer built for technical books and research papers.¹⁴⁷ It suits people who spend more time studying a document than filling in forms. Its appeal for privacy is a reading workflow built around files on your computer, with reading data stored in local databases.⁵

Last checked October 28, 2026.

At a glance

• What it is: A PDF viewer for technical books and research papers.¹
• Works on: Windows, macOS and Linux through official desktop packages.²
• Price: Free.⁷
• Licence: GNU General Public License version 3 (GPL-3.0).⁴
• Best for: Students, researchers and anyone regularly reading long PDFs.
• Official site: sioyek.info

What Sioyek does and how it protects your privacy

Sioyek helps you follow a difficult document without repeatedly losing your place. Its Smart Jump feature can find referenced figures and bibliography entries even when the PDF has no clickable links.² That is useful when a paragraph refers to a diagram many pages away: you can concentrate on the explanation instead of remembering page numbers.

The privacy benefit is practical rather than mysterious. Sioyek documents two database files for its saved reading information, including document locations, bookmarks and portals.⁵ A portal connects two places in your reading material. For a private study setup, keep the PDFs and their reading data in folders you control, and decide deliberately whether to add synchronization.

Sioyek remains under development: its development branch received a commit on October 22, 2026.⁸ GitHub still labels version 2.0.0 as the latest stable release; its downloadable files are dated December 16, 2022.³ These are different measures of maintenance, so choose a package for the features it actually contains.

Sioyek key features

• Quick Open: Search for a document you previously opened instead of finding its folder again.²
• Contents search: Find a chapter through a searchable table of contents.²
• Reference previews: View a figure or reference without leaving the current passage.¹
• Portals: Keep linked material visible in a second window while reading.¹
• Searchable highlights: Return to marked passages through a search rather than page-by-page scrolling.⁷
• Command palette: Look up available commands and shortcuts from a searchable menu.¹
• Configurable controls: Change shortcuts and selected interface settings in user configuration files.²

Sioyek pros and cons

Pros

• The focus on sustained reading makes it a promising choice for a study desk.
• Reference previews help keep an explanation and its supporting material mentally connected.
• A searchable command menu gives you a useful place to start learning.
• Free software makes it easy to try one familiar textbook before changing your routine.

Cons

• Expect some learning time if you prefer a toolbar for every action.
• Changing controls involves editing configuration files, which may feel unfamiliar.²
• The sioyek3 alpha release has an incompatible database format and carries an explicit backup warning.³
• Flathub supplies a community package that is not verified by or supported by Sioyek’s developer.⁷

Is Sioyek safe and private?

Flathub identifies Sioyek’s developer as Ali Mostafavi.⁷ Its source is publicly available under GPL-3.0.⁴ Open source means people can inspect and modify the code under its licence. Treat that transparency as a useful property, rather than a guarantee that every document is safe to open.

Pay particular attention to online lookup actions. Sioyek can search selected text or a paper’s name through Google Scholar and other external search engines.⁵ Using an external search means handing the query to that service. For confidential material, keep names and sensitive phrases out of those lookups. Prefer searching within the PDF when that answers your question.

The settings also include optional startup update checking.⁶ For a reading setup intended to stay offline, review that setting alongside external-search shortcuts. Keep a separate reminder to check for updates if you turn automatic checking off.

Sioyek allows its shared database to sit in a synchronized folder, so synchronization depends on the folder service you choose.⁶ Consider both the PDFs and their reading records when deciding what to back up. For sensitive documents, use device encryption and a separate computer account where appropriate; do not assume that choosing a local reader supplies those protections.

How to get started with Sioyek

1. Get the official download. Follow the project’s GitHub releases page for its Windows, macOS or Linux package.² Start with the stable release unless you specifically need an experimental build.
2. Open a familiar PDF. Press o to choose a file, or drag it into the window.⁵ Start with something ordinary rather than your most sensitive document.
3. Try navigation before customizing. Use the arrow keys or mouse wheel to move around.⁵ Spend a few minutes finding the controls that feel comfortable.
4. Find commands when needed. Press : to open the searchable command menu.⁵ Learn a few useful actions before trying to memorize a long shortcut list.
5. Review privacy-related settings. Use prefs_user from the command menu to open your user preferences.⁶ Decide whether you want startup update checks, external lookups or a synchronized database folder.

Who should use Sioyek, and who might prefer something else?

Choose Sioyek if you regularly study long PDFs and want to build a comfortable reading routine around them. Give it one complete reading session before deciding: try following references, returning to a passage and finding something you marked. The best reason to adopt it is that those everyday tasks become easier for you.

For a simpler Windows reading routine, consider SumatraPDF. If handwritten notes matter more, look at Xournal++; if your priority is organizing research and citations, consider Zotero. Choose around the task you repeat most often, rather than collecting features you rarely need.

Frequently asked questions about Sioyek

Is Sioyek free?

Yes: Sioyek is available free.⁷ There is no need to buy a service just to try the reading workflow described here.

Can Sioyek keep reading data on my computer?

Yes: its documentation describes local database storage.⁵ Keep those files outside synchronized folders if you want that reading setup to remain local, and take care with external searches.

Is Sioyek still maintained?

Yes: October 2026 development commits show continued maintenance.⁸ The age of the stable download still matters when comparing packages; development activity alone does not update an installed copy.

Sources

1. Sioyek: official website and features
2. Sioyek on GitHub: project README and installation
3. Sioyek on GitHub: stable and alpha releases
4. Sioyek on GitHub: GNU General Public License
5. Sioyek documentation: usage and data storage
6. Sioyek documentation: configuration
7. Flathub: Sioyek listing
8. Sioyek on GitHub: development commit history