DjVu vs PDF: Which Format to Choose for Scans and Books
The very same scanned textbook can exist both as a lightweight 3 MB .djvu and as a bloated 80 MB PDF. Does that mean DjVu is always better? Not quite. We break it down point by point — size, quality, support, search and printing — and finish with a clear answer on what you should pick.
Two formats, two destinies
At first glance DjVu and PDF are near twins: both show document pages one after another. But they were born for different purposes. PDF (1993, Adobe; now the ISO 32000 standard) was designed as a universal format for any document — from a contract with a digital signature to a glossy magazine with vector graphics. DjVu (1996–2001, AT&T Labs) was from the start a narrow tool for one job — compressing scanned paper as hard as possible.
Everything else flows from that difference in their DNA — it's why DjVu ends up lighter and why PDF ends up more convenient. What follows is point by point, with no cheerleading for either side.
File size: which is lighter
Here DjVu holds a historical edge. Thanks to layer separation (sharp text apart, blurry background apart), a scan in DjVu has traditionally weighed a fraction as much. The numbers: a 600-DPI page in DjVu is around 30–50 KB, while the same scan assembled into a PDF from ordinary JPEGs easily tops 500 KB. Across a thick book, the gap turns from megabytes into tens of megabytes.
But there's an important caveat that often goes unsaid. Modern PDF can do the same trick — a technology called MRC (Mixed Raster Content) also splits the scan into layers. A well-built MRC PDF closes in on DjVu: the size difference can be as little as 10–20%. So DjVu's crushing 2000s advantage is now far more modest — it mainly shows up against "naive" PDFs made of uncompressed images.
Verdict on size
DjVu is smaller — that's a fact. But if your PDF is built the modern way (MRC + OCR), the difference is no longer critical. Size has stopped being the decisive argument against PDF that it was twenty years ago.
Scan quality and readability
A common misconception: "a scan gets worse in PDF than in DjVu." Not true. Quality is set by the original scan, not by the container it's packed into. If a page was scanned at 600 DPI, it stays 600 DPI in both DjVu and PDF — the text is equally sharp.
The only difference is how the data is compressed. DjVu and MRC PDF keep text in a crisp bitonal layer, so letters stay sharp. A "naive" PDF made from JPEGs can slightly smear letter edges because of JPEG artifacts, especially on small type. But with a proper DjVu-to-PDF conversion the page is carried over with no lossy re-encoding — the text doesn't suffer.
Device support
Here PDF wins by a landslide, and this is the key practical argument. PDF opens literally everywhere: in any browser, on any phone, in any operating system, with nothing to install. You send a PDF and you know for sure the person on the other end can open it.
With DjVu it's trickier. You almost always need a separate reader app (WinDjView, SumatraPDF, MacDjView, mobile apps). Browsers dropped DjVu plugins long ago. Sending a .djvu to a colleague or client is a near-guaranteed "what do I open this with?" For sharing files, that's a serious downside.
A practical note
If a file needs to be sent to someone, shown from a phone, or opened on someone else's computer — pick PDF. A DjVu without a preinstalled reader often simply won't open, and you'll waste time explaining which app to download.
Search, printing and signatures
Text search. Both formats support an invisible OCR layer — you can search and copy text. A tie, with the caveat that the layer must be added when the file is created. Both DjVu and PDF are full of documents without OCR — then they're just images.
Printing. PDF was created partly for print shops, and it prints flawlessly on any printer. DjVu is harder to print: you need a reader that can hand pages to the printer correctly, and the result can be finicky.
Forms and signatures. Here DjVu is simply out of the running — it can't do this at all. PDF supports fillable fields, digital signatures and comments. For business documents there's no alternative to PDF.
Side-by-side comparison
| Criterion | DjVu | |
|---|---|---|
| Scan size | Smaller | A bit bigger |
| Opens without a reader | No | Yes |
| Browser support | No | Yes |
| Text search (OCR) | Yes* | Yes* |
| Printing | Finicky | Flawless |
| Forms and signatures | No | Yes |
| Format development | Frozen | Active (ISO) |
* — provided the OCR layer was added when the file was created.
What to choose in the end
There's no one-size answer of "always X," but the logic is simple:
- Choose PDF if the file needs to be shared, read across devices, printed, filled in as a form, or signed. That's 95% of everyday scenarios.
- Keep DjVu if you store a huge collection of scans and every megabyte counts, or if a specific archive or community works in DjVu and requires it.
In practice, most people find it easier to convert DjVu to PDF once and forget special readers forever. Scan quality doesn't suffer, and the file opens anywhere.
Turn DjVu into a universal PDF
Upload a .djvu and get a PDF that opens on any device, with no loss of scan quality. Free and right in your browser.
Want to understand the technology first? Read what DjVu is and how it works, or the practical guide on converting DjVu to PDF while keeping the OCR. All available conversions are on the formats page.
