Mozilla PDF.js vs Okular
Mozilla PDF.js
mozilla.github.io
Okular
okular.kde.orgSide by side
| Figure | Mozilla PDF.js | Okular |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Web | Yes | — |
| Windows | — | Yes |
| macOS | — | Yes |
| Linux | Yes | Yes |
| API | Yes | — |
| Self-hosted | Yes | — |
| Plans published | 1 | 1 |
| Spec score · File Reader Software | 8.2 (#8) | 8.3 (#7) |
| Spec score · PDF Readers | 8.3 (#8) | 8.3 (#9) |
| Annotations | PDF.js renders annotations for viewing and supports adding a subset of annotation types. | Annotation mode adds inline and popup notes, highlighting, underlining and text. |
| Annotation tools | Yes | Yes |
| Distribution | Prebuilt builds are available, and the project lists jsDelivr, cdnjs, and unpkg as CDNs hosting PDF.js. | Linux packages are available through distribution software stores, Flatpak is available from Flathub, and Microsoft Store is the recommended Windows installation source. |
| Form filling | Yes | Yes |
| Free plan | Yes | Yes |
| License | PDF.js is licensed under Apache 2.0, and its documentation is licensed under CC BY-SA 2.5. | Okular is released under the GPLv2+ and its source code is available in KDE's GitLab repository. |
| Platform support | web | Okular is described as multi-platform. |
Plans
In their own words
Mozilla PDF.js
Mozilla PDF.js is a free, web standards-based platform for parsing and rendering PDF files. Developers can use its display API to render documents and retrieve information, or adapt the viewer layer for a custom interface. That viewer is used in Firefox and project browser extensions. PDF.js renders annotations and supports adding a subset of annotation types, and it supports form filling; OCR is not provided. The project targets HTML5-compliant browsers and includes a legacy build for older browsers, although PDF feature support varies by browser and version. Prebuilt builds are available, with hosted copies listed through jsDelivr, cdnjs, and unpkg. Developers can clone and build it locally, but some browsers require a local web server instead of opening PDFs through file URLs. Cross-origin requests are blocked by default, so CORS or a server proxy may be needed. For large documents, rendering only visible pages can reduce memory use. PDF.js is licensed under Apache 2.0.