Okular vs Mozilla PDF.js

Okular9.2Visit Mozilla PDF.js8.8Visit

Higher score Okular #2 in PDF Readers 9.2/10 Free plan Free plan✓ 3 of 4 features Visit KDE

vs

Mozilla PDF.js #5 in PDF Readers 8.8/10 Free plan Free plan✓ 2 of 4 features Visit Mozilla PDF.js

• Okular fits best

  Free open-source desktop PDF reading

• Mozilla PDF.js fits best

  Web and application developers

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Side by side

Feature	Okular 9.2/10 Visit ↗	Mozilla PDF.js 8.8/10 Visit ↗
At a glance
Editor score	9.2	8.8
Ranking	#2 in PDF Readers	#5 in PDF Readers
Best for	Free open-source desktop PDF reading	Web and application developers
Pricing model	Free	Free
Starting price	Free plan	Free plan
Free plan	✓	✓
Free trial	—	—
Deployment	Desktop	Self-hosted
Platforms	Windows, macOS, Linux	Web
Built for	Solo, Small business, Mid-market, Enterprise	Solo, Small business, Mid-market, Enterprise
Features Okular 3/4 · Mozilla PDF.js 2/4
Annotation tools	✓	✓
Form filling	✓	✓
Offline access	Not checked yet	Not checked yet
Text-to-speech	✓ (best)	Not checked yet
Specs
OCR support	Not checked yet	None
Platform support	Cross-platform	Web
Our review
Pros	Free and open source across Windows, macOS and Linux Annotations, form filling and digital-signature support Text-to-speech, presentation mode and multi-format viewing	Open-source PDF parsing, rendering, search, and browser viewing Annotation editing includes highlights, free text, ink, stamps, and signatures Supports npm, CDNs, APIs, self-hosting, and Firefox and Chrome extensions
Cons	No OCR capability is included No integrations are supplied Focused on desktop platforms rather than broader access	Requires developer integration rather than serving as a conventional end-user app Its focus is PDF viewing, parsing, forms, and annotations Interactive scripting is centered on PDF form calculations and actions
Our verdict	Okular is a free, open-source document viewer from KDE for people who need more than basic PDF reading on a desktop. It opens PDFs alongside PostScript, TIFF, DjVu, images, XPS, EPUB, comic-book formats and other documents. Navigation… Read the review →	Mozilla PDF.js is an open-source JavaScript library and browser-based viewer for parsing and rendering Portable Document Format files. It is aimed at web and application developers who need to embed PDF capabilities in web applications or… Read the review →

Strengths and trade-offs

• Okular — where it wins

  • Free and open source across Windows, macOS and Linux
  • Annotations, form filling and digital-signature support
  • Text-to-speech, presentation mode and multi-format viewing

  Where it doesn't

  • No OCR capability is included
  • No integrations are supplied
  • Focused on desktop platforms rather than broader access

• Mozilla PDF.js — where it wins

  • Open-source PDF parsing, rendering, search, and browser viewing
  • Annotation editing includes highlights, free text, ink, stamps, and signatures
  • Supports npm, CDNs, APIs, self-hosting, and Firefox and Chrome extensions

  Where it doesn't

  • Requires developer integration rather than serving as a conventional end-user app
  • Its focus is PDF viewing, parsing, forms, and annotations
  • Interactive scripting is centered on PDF form calculations and actions

• Okular9.2/10 · Free plan

  A capable open-source desktop reader with annotations, forms, signatures and accessibility tools.

  Visit KDEFull verdict →
• Mozilla PDF.js8.8/10 · Free plan

  A developer-focused PDF viewer and rendering platform for web applications.

  Visit Mozilla PDF.jsFull verdict →