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DJVU format guide

A .djvu file is a scanned-document image container that compresses book and magazine pages far smaller than equivalent PDFs by splitting each page into layers. It is a reading and archiving format rather than an editing one, and because no browser decodes it natively, this site documents .djvu without offering conversions for it.

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Where DJVU comes from

Researchers at AT&T Labs — including Yann LeCun, Leon Bottou, Patrick Haffner, and Paul Howard — developed DjVu in the late 1990s, publishing it in 1998 as a web-era answer to bulky scanned documents. Rights passed through LizardTech and later Japanese owners, while the open-source DjVuLibre project has kept free encoders and decoders alive.

How DJVU works

  • Uses mixed raster content: a JB2-coded bilevel mask holds text and line art, while IW44 wavelets code the background and foreground colors at lower resolution
  • JB2 exploits repeated glyph shapes across a page, shrinking dense text dramatically
  • Multi-page documents share dictionaries between pages for further savings
  • An optional hidden text layer stores OCR output for searching and selection
  • Typical scanned pages run 3-10x smaller than comparable image-based PDFs

When to use DJVU

  • Digitized book and journal archives, notably in library and academic collections
  • Distributing high-page-count scans where PDF sizes would be prohibitive
  • Preserving searchable OCR text alongside exact page images

Strengths and limitations

Strengths

  • Exceptional compression for scanned text pages
  • Keeps crisp, legible text at high zoom thanks to the separate bilevel layer
  • Open-source tooling exists via DjVuLibre

Limitations

  • No native support in any browser or mainstream OS viewer
  • The wavelet and mask layers discard information, so it cannot round-trip source scans exactly
  • The format's ecosystem has stagnated, and PDF/A has won the archival mindshare battle

Compatibility

Reading .djvu requires dedicated software: DjVuLibre's djview, SumatraPDF on Windows, or mobile reader apps, since neither browsers nor stock OS viewers open it. Conversion to PDF or page images must happen in desktop tools such as DjVuLibre's ddjvu — browser-based converters, including this one, cannot decode the format.