Over the past 20 years digital comics reading has grown through services like Comixology, DC Universe Infinite and Marvel Unlimited. And it’s gained significant acceptance through iPads and other tablets.
At the grass-roots level, collectors have shared scans* of comic books for just as long. The benefit of many users sharing their public domain or scarce vintage books is that we can all fill in a collection that would take many lifetimes to find, let alone afford.
If you’re just an occasional digital reader, looking at a folder of scans in any image viewer is likely to provide you a perfectly adequate reading experience. Similarly, some digital publishers save their books as PDFs, and PDF viewers abound on each platform.
Digital Comic Formats
The two most common file formats for digital comics are CBZ and CBR. Respectively, they stand for Comic Book Zip and Comic Book Rar. Both use the compression schemes in their names, and behind their extension names the files are archives. Change a .cbz to .zip or a .cbr to .rar and you can unpack the archive with a utility. Once unpacked you’ll have a folder and inside will be a series of sequential image files, most commonly JPGs.
The benefit of a CBZ or CBR file is that it’s one lightweight file for a reader to unpack on the fly and display on your device. By comparison, PDFs come with considerable overhead, both in the PDF file and in Adobe Reader. You’ll notice larger file sizes, higher memory usage and slower display times. On battery-operated devices that also comes with a bigger drain on battery life.
YACReader
Once you move beyond the occasional digital comic, having a dedicated reader app is a good thing. I recommend YACReader (Yet Another Comic Reader) which is free, simple to use and regularly updated. It is available for Windows, Mac, iOS and Linux.
It’s as easy to use as selecting a CBZ, CBR or PDF file and having YACR open it for you. I won’t go into app operation here. The YACR site gives you all the details.

YACReader Library
The nice thing about YACR is that it scales with you. Once you have a lot of digital comics, you can import them all into YACR Library, a separate included app for desktop. Whatever file folder structure you set up on your desktop, that it what is mirrored inside the Library. The Library is also lightweight, serving only as a manager. Your comics stay where you’ve stored them on your drive.
The Library also has utility functions to transfer comics to your iOS device, and the Library Server is suited for embedded devices like NAS.

If you end up using and liking YACReader, please consider giving the developer (a one-man operation) a donation on his site. It helps pay for development and web costs.
Also, I highly recommend ComicBookPlus for free vintage public domain comic book scans. They also work on a donation model. Help support the work of hundreds of people who have shared their scans.
*I neither advocate for nor condone the distribution or downloading of currently copyrighted materials.
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