Read a .cbz or .cbr comic in your browser

What it shows

• Every page, in the order the scanner meant. Page pictures sorted the way people number them: page2 before page10, and chapter folders in order (Ch 2 before Ch 10). macOS __MACOSX copies, .DS_Store and Thumbs.db are skipped; any other file that is not a picture is named below the reader.
• Fit width or fit height. Fit width fills a phone screen and lets you scroll down the page; fit height shows the whole page at once on a computer.
• Two pages side by side. The cover stays on its own, then pages 2 and 3, 4 and 5, as in the printed book. A double-page picture (wider than tall, or marked DoublePage in ComicInfo.xml) gets the spread to itself, so the pairs after it stay right.
• Turning pages. Swipe, tap the left or right side of the page, use the ← and → keys (Home and End jump to the first and last page), the buttons, the page slider, or the thumbnail strip. “Page 7 of 24” is always shown.
• Right to left for manga. One switch mirrors the keys, swipes, taps, spreads and thumbnails. A comic whose ComicInfo.xml says <Manga>YesAndRightToLeft</Manga> opens that way by itself.
• The credits. Series, number (of how many), volume, title, date, writer, artists, publisher, genre, language and summary, from the ComicInfo.xml file inside, when there is one.
• Save one page. The picture as it is stored in the archive, with its own name, for a wallpaper or to send to a friend.

What is inside a .cbz or .cbr file

A comic book archive is an ordinary archive of pictures with a different extension: .cbz is a ZIP, .cbr a RAR, .cb7 a 7-Zip archive and .cbt a tar. The names were popularised by CDisplay, an early Windows comic reader, and every comic reader since accepts them. There is no index of pages: the order is the alphabetical order of the file names, which is why scanners pad page numbers with zeros (001.jpg, 002.jpg). When they do not, a plain alphabetical sort puts 10.jpg right after 1.jpg; this reader compares the numbers in names as numbers, so unpadded names still come out right.

Because the extension and the contents are set separately, mislabelled files are common: many .cbr files are really ZIPs and some .cbz files are RARs. viewhack reads the first bytes (PK for ZIP, Rar! for RAR, 7z¼¯' for 7-Zip, ustar at byte 257 for tar), opens the file whatever its name says, and tells you which it is.

Many comics also carry a ComicInfo.xml file, a format from the ComicRack reader that tools such as ComicTagger, Mylar, Komga and Kavita still write. It holds fields like <Series>, <Number>, <Count>, <Writer>, <Penciller> and <Summary>, a <Manga> field (No, Yes, or YesAndRightToLeft for right-to-left reading), and a <Pages> list that can mark the cover and double-page spreads.

How it opens a 300-page comic quickly

Pages are unpacked only when they are needed: the page on screen, the next two, and the thumbnails as they scroll into view. A ZIP's directory at its end says where each page is, so a .cbz page is read straight from its place in the file and inflated by the browser. RAR and 7-Zip files are read by libarchive compiled to WebAssembly, which holds the whole archive in the tab's memory (up to 2 GB). In a solid RAR or a 7-Zip archive, pages are compressed as one stream, so a page near the end takes longer, because everything before it is unpacked first. JPEG, PNG, GIF, WebP, AVIF and BMP pages are drawn by the browser; JPEG XL pages, which most browsers cannot show yet, are decoded by a WebAssembly build of libjxl.

Files it opens

.cbz

A ZIP of pages. The most common comic format, written by ComicRack, Calibre, Kavita, Komga, manga downloaders and most scanners.

.cbr

A RAR of pages, RAR 4 or RAR 5. Common for older scans.

.cb7 and .cbt

A 7-Zip archive or a tar of pages. Rare, but every reader accepts them.

.zip, .rar, .7z, .tar

Dropped on this page, a plain archive of pictures is read as a comic too. On the front page a plain archive opens in the archive viewer instead, which lists every file.

What this cannot do

• Open DRM-protected comics. Comics bought in Kindle, comiXology, Marvel Unlimited or similar apps are encrypted for that app and are not .cbz or .cbr files. Only DRM-free files open here, such as those from Humble Bundle, DriveThru Comics or a publisher's own shop, and your own scans.
• Read PDF comics. A comic sold as PDF opens in the browser's own PDF viewer: open it in a new tab.
• Edit, tag or convert. It only reads. It does not change the archive, write a ComicInfo.xml, or convert between .cbr and .cbz.
• Open password-protected archives. Encrypted RAR and 7-Zip files cannot be decrypted here. A password-protected .cbz opens in the archive viewer, renamed to .zip.
• Remember where you stopped. Nothing is stored in the browser, so a comic opens at page 1 again next time. Note the page number shown.
• Read .cba or ACBF comics. ACE archives (.cba) are not read, and the panel-by-panel information in Advanced Comic Book Format files is not used, although their pages still show if the archive is a ZIP.
• Join multi-part RAR files. A comic split into .part1.rar, .part2.rar and so on shows only the pages that sit wholly inside the part you open.