What Are CBZ and CBR Files?
Make a copy of issue-01.cbz and rename the copy to issue-01.zip. Open it, and the pages are there as separate image files, listed in name order.
Nothing was converted. A CBZ or CBR file is a folder of page images packed into a ZIP or RAR archive, with a comic-book extension on the name.
Work on a copy, so the original keeps its name.
The pages inside
The MobileRead wiki, a wiki about e-readers and their file formats, calls CBR and CBZ container formats for comic books, manga and other image-heavy books.
The pages are ordinary picture files. They are usually JPEG, PNG, GIF, TIFF or, more recently, WebP. Not all readers support all of those image types.
There are no text files in the basic form. The reader shows the images in alphabetical order of their file names.
That is why pages are named page-001, page-002 and so on. Without the leading zeros, page-10 would sort before page-2.
The pages are pictures, so nothing reflows to fit the screen the way text does in an ePub file. A scan stored as a DjVu file is also made of page images.
ZIP or RAR
The last letter of the extension tells you the archive type. Comic Book Z is a ZIP file. Comic Book R is a RAR file.
Inside, the two are the same kind of thing: a pile of page images. The main difference is how the pile is packed.
Because they really are ZIP and RAR files, some readers can look at the contents if the extension is renamed.
Most readers can handle either format, but there are exceptions. Metadata is one place where they differ: ComicBookInfo data is stored in the ZIP file header as a comment, so it belongs to CBZ.
What opens them
Kobo and SumatraPDF open both formats, and Calibre accepts both for conversion. KOReader lists CBZ but not CBR.
- Kobo: the current Kobo devices can read CBR and CBZ files.
- SumatraPDF: free and open source.
- KOReader: an open-source reader app for e-readers and Android.
- Calibre: its conversion output formats include ePub, AZW3 and PDF.
The kind of comic matters too.
US comic books are usually in color with very small print, and they typically need a zoom mode on a smaller screen.
Manga is typically black and white with larger lettering in its text bubbles, and it suits a standard e-book reader.
Repacking a CBR as a CBZ
A CBR is a RAR of images, and a CBZ is a ZIP of the same kind of images. So repacking is three steps.
- Unpack the CBR into a folder of page images.
- Check that the file names still sort in page order.
- Put the images into a ZIP archive, then change the extension from
.zipto.cbz.
The pages are not touched, so the image quality stays the same. Only the archive around them changes.
Keep the original CBR until the new file opens correctly in your reader.
When you pack pages yourself, make a CBZ.
Reading a CBR you already have needs no change on a Kobo or in SumatraPDF, and Calibre can convert it. Repack only when a reader refuses the file.