Why tapping the file does nothing
iPhone and iPad ship with viewers for PDF, images, and office documents, but not for comic archives. No system app claims .cbz, and a website cannot register itself as the handler for a file type. A tap offers sharing options, not reading.
Quick Look can preview individual images after you extract an archive, which is not the same as reading a comic in order.
Step by step
- Get the file into the Files app: from Mail, tap the attachment and choose Save to Files; from a computer, use AirDrop; from a cloud provider, open it in Files.
- Check that it is really downloaded. An iCloud item with a cloud icon is a placeholder, and the picker will stall or refuse until it is local. Tap the cloud icon first.
- Open this site in Safari, tap Choose a CBZ file, then Browse and pick the archive from On My iPhone or iCloud Drive.
- If the file arrived as a .zip, rename it in Files (long-press, Rename, replace .zip with .cbz). The bytes are already a ZIP, so no conversion is needed.
- Add the site to your Home Screen if you expect to come back. It still opens the same picker, but saves typing the address.
Where the file can live
On My iPhone is the simplest location because it is always local. iCloud Drive works, but only after the file is downloaded. External drives and SD cards appear in Files on modern iOS and iPadOS, which is useful for large scan archives that would otherwise fill local storage.
Third-party providers such as Dropbox or Google Drive appear in the Files browser once their Files extension is enabled. Picking from one may trigger a download before the reader can open the archive.
iOS limits you will actually notice
- No file association for .cbz, so the site has to be opened first. This is an OS rule, not a site limitation.
- The file picker filters by declared types. iOS greys out files when the filter is too specific, so this reader relaxes the filter on iOS and shows every file instead.
- Safari gives each tab a memory budget. Very large pages are downsampled before display; without that, a 5000-pixel scan can exhaust a phone tab.
- Switching apps under memory pressure can discard the page. Reading progress is stored locally and restored, but the browser is not allowed to reopen your file by itself, so you pick it again.
- Private browsing can clear local progress when the session ends.
iPad specifics
Wide screens make double-page mode useful, and an external keyboard gives you arrow-key page turns. Split View and Slide Over shrink the memory available to the tab, so a huge archive is more likely to be reloaded there than in full screen.
When a native app is the better tool
If you keep a large library on the device, a native comic app handles file association, folders, and offline covers better. A browser reader is for opening one file quickly, on a device where you do not want to install or sign in to anything.