Mozilla PDF.js vs Skim
Mozilla PDF.js
mozilla.github.ioSkim
skim-app.sourceforge.ioSide by side
| Figure | Mozilla PDF.js | Skim |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Web | Yes | — |
| macOS | — | Yes |
| Linux | Yes | — |
| API | Yes | — |
| Self-hosted | Yes | — |
| Plans published | 1 | 1 |
| Spec score · PDF Readers | 8.3 (#8) | 7.4 (#17) |
| Annotation tools | Yes | Yes |
| Free plan | Yes | Yes |
| Integrations | PDF.js is built into Firefox 19 and later, and the project provides a Chromium browser extension. | Skim lists interaction with LaTeX, SyncTeX, and PDFSync, as well as integration with BibDesk and other third-party applications. |
| Platform support | web | desktop |
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.