andreasgal/pdf.js
stale
significant_divergence
Selected Prefer upstream unless you explicitly need a frozen historical PDF.js snapshot. This fork is only attractive for legacy preservation or archaeology; for active product use, its age and divergence are major liabilities.
ChineseDron/pdf.js
stale
significant_divergence
Prefer this fork only if you need a legacy, highly customized PDF.js baseline and are willing to own the maintenance burden. For most adopters, current upstream is the safer choice because this fork is extremely stale and appears to have lost a lot of later upstream coverage and fixes.
mainegreen/pdf.js.forms
stale
significant_divergence
Choose this fork only if PDF form handling is the primary requirement and you are prepared to own a heavily stale codebase. If you want current PDF.js improvements, this fork is too far behind upstream to be a low-risk adoption.
IsaacSchemm/pdf.js-seamonkey
stale
significant_divergence
Choose this fork only if SeaMonkey-class browser support is the requirement. For general PDF.js adoption, upstream is the better default because it is far more current, actively maintained, and likely more complete.
operasoftware/pdf.js
stale
significant_divergence
Prefer this fork only if you need the old Opera-specific baseline and its historical regression coverage. For any new work, upstream mozilla/pdf.js is the better choice because this fork is heavily stale and far behind current capability.
arturadib/pdf.js
stale
significant_divergence
Prefer upstream for any active product. Choose this fork only if you specifically need the old 2012 behavior plus its small set of viewer fixes and can accept substantial maintenance and compatibility risk.
Adopt this fork if you need Zotero-oriented reading, reference extraction, and scan/blending behavior that upstream PDF.js does not provide out of the box. Avoid it if you want the broadest upstream compatibility and the lowest long-term maintenance burden.
Globe-Engineer/pdf.js
stale
significant_divergence
Choose this fork only if the chat-assisted reader workflow is the product. If you need a current, low-risk PDF.js base, upstream is the better default because this fork is materially stale and highly divergent.
zen-browser/pdf.js
stale
significant_divergence
Choose this fork only if you specifically need its Zen Browser-specific tweaks and can own the maintenance burden. If you want current PDF.js capabilities, broader coverage, and lower risk, upstream is the safer choice.
Prefer this fork only if you need a mostly upstream PDF.js base with no meaningful downstream changes. If you want new capabilities or the latest upstream fixes, this snapshot is not compelling because it is materially behind upstream and adds nothing visible of its own.