Show the Working

ZIP to CBZ

Your comic never leaves your browser, and nothing is downloaded to make this work. A comic can be hundreds of megabytes, which is the other reason not to upload one.

…or drop one anywhere on this page.

A folder of pictures, turned into something a comic reader opens.

The pictures are put in the order a person would put them in, renumbered, and stored uncompressed — which is what comic readers expect, and which costs nothing because a JPEG is already compressed. Deflating one spends time to make the file very slightly larger.

page10 comes after page9, and that is the whole job

A .cbz has no specification. It is a ZIP of pictures, the format was invented by readers rather than published by anybody, and the page order is the order of the filenames. That sounds simple until you sort them.

Sorting filenames as text compares them one character at a time, so page10 comes before page2 — "1" is less than "2" and nothing looks any further. A comic converted that way reads page 1, page 10, page 11, all the way to page 19, then page 2. It is not subtly wrong; it is unreadable. And that sort is the one every programming language gives you for free, which is why so many free comic converters do it.

This compares runs of digits as numbers, shows you the order it worked out, and shows what the naive sort would have given alongside — so you can see the difference rather than take it on trust. Mixed padding is handled too: p1, p02 and p010 in one archive sort by their value.

What it will not open, and why

A .cbr, which is a RAR archive. Nothing on this site opens one and nothing ever will: RARLAB's licence forbids using their code to re-create the algorithm. That is a legal restriction rather than a technical difficulty, and it is worth the distinction — the format is not hard, it is closed. Unpack it with a program licensed for it and re-zip the pictures.

A .cb7 is a 7z, which needs the LZMA compressor. A browser does not have one, so opening it here would mean downloading a compressor — the thing this site does not do. Both are recognised from their first four bytes and named, rather than refused without a reason.

Anything in the archive that is not a picture is left behind, including a folder structure — a comic is a flat list of pages and nothing else.

Where to go next