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Document Format

DjVu

Déjà Vu (Scanned Document Format)

DjVu (pronounced 'déjà vu') is a digital document format developed by AT&T Labs specifically for scanned books, magazines, and academic papers. It uses sophisticated foreground/background separation to compress scanned pages dramatically — a 500-page scanned book that would be 50 MB in PDF can fit in 2 MB as DjVu. Despite its technical merits, DjVu remained niche due to lack of mainstream support.

What is DjVu?

DjVu separates each scanned page into three layers: foreground (text and line art at high resolution), background (page texture and continuous-tone images at low resolution), and a mask that combines them. The text foreground is compressed with a wavelet-based codec optimized for sharp edges; the background uses a different wavelet codec optimized for smooth tones. The result is excellent text legibility at very small file sizes.

DjVu pros and cons

Advantages

  • Extremely small file sizes for scanned documents — often 10× smaller than PDF
  • Excellent text legibility even at low compression
  • OCR text layer support for searchable documents
  • Free, open-source reference implementation (DjVuLibre)
  • Multi-page document support with hyperlinks and annotations

Limitations

  • Almost no native browser support
  • Few e-readers handle DjVu (some Onyx Boox models do)
  • Limited support on iOS and Android
  • Requires plugin or app to view
  • PDF has won the universal document race

When should you convert DjVu files?

Convert DjVu to PDF for universal accessibility — every device reads PDF without plugins. The PDF will be significantly larger (5–10×) than the DjVu, but compatibility is worth the size penalty for shared documents. For your own archive where you have DjVu reading software, keeping the DjVu format saves substantial storage.

Convert DjVu files

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DjVu FAQ

How do I open a DjVu file?
Windows: WinDjView, Sumatra PDF, or STDU Viewer. macOS: MacDjView (free) or Preview with a plugin. Linux: DjView (DjVuLibre). iOS/Android: dedicated DjVu reader apps. Most general-purpose readers don't support DjVu.
How do I convert DjVu to PDF?
Using DjVuLibre command line: `ddjvu -format=pdf input.djvu output.pdf`. Using Python djvu2pdf: `pip install djvu2pdf && djvu2pdf input.djvu output.pdf`. Using Calibre: add the DjVu, click Convert books, choose PDF as output.
Why isn't DjVu used more widely?
Network effects — PDF achieved critical mass before DjVu's compression advantages mattered to most users. PDF is built into every browser, OS, and device; DjVu requires a deliberate install. The compression advantage matters mainly for academic archives and free-content libraries, which is where DjVu still thrives.

More formats

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