Okular

Overview

Okular is a free document viewer for people whose reading spans PDFs, ebooks, comics, images and other file types. Its mix of annotation, form filling and PDF signature tools makes it more capable than a read-only viewer, but the lack of OCR rules it out for text recognition in scans.

Released under GPLv2+, Okular is associated with KDE and runs on Linux, Windows and macOS, as well as other platforms including BSD. Its broad format support is the main draw: one application can cover varied reading and viewing tasks without a paid tier.

Key features

Documents, images and comics

Okular handles PDF, EPUB, DjVu, PostScript, TIFF, DVI, XPS, FictionBook, Plucker and fax files, along with Markdown, images and CBR or CBZ comics. That breadth suits readers with mixed libraries; it is less compelling if the only requirement is a narrow, specialized workflow. It can display Markdown, browse images and read comics and ebooks alongside conventional documents.

Selection, annotation and signatures

Selection tools can copy text, areas and tables, while a magnifier enlarges small text. Annotation mode adds inline or popup notes, highlights, underlining and text. Form filling and text-to-speech extend its usefulness beyond passive reading, though anyone who needs OCR to extract text from scans will need another tool.

For PDFs, Okular can sign files, verify digital signatures and detect modifications. This is useful for readers who need basic signing and signature checks within their viewer, not a substitute for OCR.

Privacy and sustainability

KDE says its software does not transmit information from end-user devices unless a user explicitly acts, and telemetry is opt-in and disabled by default where offered. Okular received the Blue Angel ecolabel in 2022 for resource and energy efficiency. Those are meaningful considerations for privacy-conscious users and readers who value efficiency.

Pricing

Free Software: free (GPLv2+). Okular is fully free software, with source code available through KDE's GitLab repository. There is no paid tier to unlock its viewer or annotation tools, making it a straightforward option for individual readers who want the full software without a subscription.

The site also accepts donations to KDE through PayPal and other methods. Donations are optional; they do not change the free-software license.

Platforms

Okular supports Linux, Windows and macOS, as well as other platforms including BSD. Linux packages are available through distribution software stores, with Flatpak on Flathub; the Microsoft Store is the recommended Windows source. Untested nightly builds are offered for Windows and macOS on ARM and Intel, so those are a less assured route than standard releases.

Who it's for

Choose Okular if you want a no-cost viewer for a varied collection of documents and media, and value built-in annotation, form filling or PDF signature checks. Its cross-platform support makes it a reasonable fit for readers moving between desktop operating systems. Look elsewhere if OCR is essential, or if your needs are limited to image viewing and a specialist image tool is a better match.

Pros and cons

• Broad format coverage: PDFs, ebooks, comics, images and Markdown can live in one viewer, useful for mixed libraries.
• Useful document tools at no charge: Annotation, form filling, text-to-speech and PDF signing and verification add practical ways to work with files.
• Cross-platform availability: Linux, Windows and macOS support makes it accessible across major desktop systems.
• No OCR: Scanned documents that need text recognition require another application.

Alternatives

• File Viewer Software and PDF Readers are category lists for comparing options by use case.
• ViewAnyFile.app is another free option, with platforms including Android, iOS and web as well as desktop systems; consider it if those platforms matter.
• XnConvert has a free option for private, educational and non-profit use, plus a company license; consider it for an image-focused workflow.
• Geeqie is free open software for Linux, macOS and Windows; consider it as another free option.
• HFSExplorer is free software for Linux, macOS and Windows; consider it if it fits your file-viewing needs.
• Universal File Opener has a free plan for supported files on Android and Windows, with file-size and compatibility limits; consider it if you use those platforms.
• Evince is a free Linux option; consider it if you only need Linux support.
• nomacs is free for private and commercial use on Linux, macOS and Windows; consider it for image viewing.
• FastStone Image Viewer offers free personal and educational use on Windows, plus a commercial lifetime license; consider it for an image-viewing workflow on Windows.

Verdict

Okular is the right choice for readers who want a free, cross-platform viewer that handles a broad mix of formats and adds annotation, forms and PDF signature tools. Its strongest reason to choose it is that range in one application; its clearest reason to look elsewhere is the absence of OCR.