Please note that there is currently an issue where iCloud sync might not work anymore on older operating systems.

Apple’s iCloud service deprecated an operation and their servers now suddenly started to return an error. For older iOS/macOS system versions, requests are somehow rejected by iCloud servers, which is a non-recoverable error. On newer operating systems, it’s just a “bad request” that gets ignored by the app.

Yomu v3.7.0 should fix this iCloud bug. Otherwise you would need to upgrade your iPhone/iPad/Mac operating system to the latest version, which should solve the problem as well.

Yomu uses Apple’s default text selection, which can sometimes be unreliable. The behaviour (and issues) are the same as when you for example select text in Safari browser.

What usually works best is to:

1. Long press on an individual word
2. Adjust the selection handles afterwards

There will likely be some optimizations in an upcoming iOS platform update. Please report this issue directly to Apple for it to be prioritized:
https://www.apple.com/feedback/

How text is displayed depends on the encoding of a book. Unfortunately, encoding for certain special characters is not always handled correctly for some older ebook formats. This can result in for example quotes, apostrophes or other characters being garbled.

It appears to be an issue in one of Apple’s components. A recent version of Yomu added a workaround that should solve the problem. But there might still be cases where it doesn’t work, please send the corresponding files to support for further investigation.

As an alternative, you can also convert such books using Calibre and reimport them, which should fix the problem as well.

1. Install calibre ebook manager
2. Add and select books to convert
3. Configure EPUB output options
   • Output format: EPUB
   • EPUB version: 2

Or you could also use the Modify ePub calibre plugin with the Encode HTML in UTF-8 option to clean up invalid encoding.

Reader menu “Look Up” and “Translate” are no longer available with iOS 17.4 because of a system level issue. They have been replaced with a “Define” action to show dictionaries and a new “Open …” option to lookup selected text on Wikipedia, translate it with Google Translate and DeepL or to query any other service.

On macOS, you can right click text to get a context menu to create highlights or notes. Context menus don’t work as expected on Monterey, but this macOS issue should be fixed with Ventura. It’s recommended to use the toolbar or keyboard shortcuts for highlights, notes or other text selection actions.

Please note that “Define” is not available on Mac because this feature is somehow not supported on that platform.

Saving images uses Apple’s Photos framework like on iOS. It only asks for the permission once, but you should be able to change it later in the settings.

But somehow the Photos permission is not available in the Mac settings anymore and can no longer be updated. Most likely this is an issue with either Apple’s framework or system settings.

As a workaround, you can reset all permissions for Yomu on Mac with the following Terminal command. You will be ask for it again the next time you save an image:
tccutil reset All net.cecinestpasparis.yomu

Due to a bug in macOS 11.4+, layout rendering for some Mac Catalyst apps no longer works as expected when an external monitor is connected. While the correct content is initially displayed, it breaks the more you scroll or change a page.

According to Apple, a system-level fix is required. It should now work again with macOS 12, but unfortunately a patch for macOS 11 will not be released. There is no workaround available and you will need to either update to macOS 12 or disconnect external displays.