KOReader vs Mozilla PDF.js

KOReader7.1Visit Mozilla PDF.js6.9Visit

Higher score KOReader #5 in File Reader Software 7.1/10 Free plan Free plan✓ 1 of 4 features Visit KOReader

vs

Mozilla PDF.js #6 in File Reader Software 6.9/10 Free plan Free plan✓ 1 of 4 features Visit Mozilla PDF.js

• KOReader fits best

  Open-source readers across ebook and document formats

• Mozilla PDF.js fits best

  Embedding a PDF reader in a web application

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Side by side

Feature	KOReader 7.1/10 Visit ↗	Mozilla PDF.js 6.9/10 Visit ↗
At a glance
Editor score	7.1	6.9
Ranking	#5 in File Reader Software	#6 in File Reader Software
Best for	Open-source readers across ebook and document formats	Embedding a PDF reader in a web application
Pricing model	Free	Free
Starting price	Not published	Not published
Free plan	✓	✓
Free trial	—	—
Deployment	Self-hosted, Desktop, Mobile	Self-hosted
Platforms	Linux, macOS, Android	Web
Support	Community, Docs	Community, Docs
Built for	Solo	Solo, Small business, Mid-market, Enterprise
Features KOReader 1/4 · Mozilla PDF.js 1/4
Annotations	✓	✓
Text search	Not published	Not published
Accessibility support	Not published	Not published
Cloud sync	Not published	Not published
Specs
Supported formats	Not published	Not published
Platforms	Kindle, Kobo, PocketBook, Android, desktop Linux; macOS emulator	Not published
Our review
Pros	Opens ebook and document formats including EPUB, PDF, DjVu, and MOBI Customizable typography, search, bookmarks, and highlights Calibre integration and optional cross-device reading-position sync	Renders PDFs in the browser with search, zoom and page navigation Supports annotations, interactive forms, printing and downloading Open source and self-hostable, with a customizable reference viewer
Cons	Platform coverage varies across e-readers, Android, Linux, and macOS emulator Progress Sync requires a separate copy of the document on each device Bookmarks and highlights are supported, but note-taking is not	Focused on PDFs rather than multiple document types No OCR support Requires developers to embed or customize the viewer and host its assets
Our verdict	KOReader is a free, open-source document reader aimed primarily at E Ink devices, with versions also available for Android and desktop Linux. It suits solo readers who want control over typography and access to ebook and fixed-page… Read the review →	Mozilla PDF.js is an open-source JavaScript technology for parsing and rendering PDF files in web applications. Its reference viewer gives developers a starting point for adding document navigation, search, annotations and interactive… Read the review →

Strengths and trade-offs

• KOReader — where it wins

  • Opens ebook and document formats including EPUB, PDF, DjVu, and MOBI
  • Customizable typography, search, bookmarks, and highlights
  • Calibre integration and optional cross-device reading-position sync

  Where it doesn't

  • Platform coverage varies across e-readers, Android, Linux, and macOS emulator
  • Progress Sync requires a separate copy of the document on each device
  • Bookmarks and highlights are supported, but note-taking is not

• Mozilla PDF.js — where it wins

  • Renders PDFs in the browser with search, zoom and page navigation
  • Supports annotations, interactive forms, printing and downloading
  • Open source and self-hostable, with a customizable reference viewer

  Where it doesn't

  • Focused on PDFs rather than multiple document types
  • No OCR support
  • Requires developers to embed or customize the viewer and host its assets

• KOReader7.1/10 · Free plan

  A format-flexible reader with annotations, PDF controls, and optional reading-position sync.

  Visit KOReaderFull verdict →
• Mozilla PDF.js6.9/10 · Free plan

  A self-hosted PDF viewer for web apps, with navigation, annotations and forms.

  Visit Mozilla PDF.jsFull verdict →