Believe it or not, one of the most common accessibility pitfalls I see in iOS apps, is forgetting to configure a suitable accessibility label for buttons with just an image (no title), resulting in VoiceOver saying just: "button".
Why for buttons with just an image? If it has a title, the accessibility label gets inferred from it. So here's one that should be very easy for you to find and fix in your app. No more apps that just say: button, button, button, button...!
If you are looking for the best explanation on what makes, not good, but great accessibility labels, I really recommend “Writing Great Accessibility Labels” by @jordyn2493 at WWDC. The difference between someone using/loving/deleting your app. https://developer.apple.com/videos/play/wwdc2019/254/
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Accessibility labels are not just for VoiceOver. If you tweak how they sound by changing spelling, adding spaces, etc. you could be making the experience worse for Voice Control and Braille display users. Attributed accessibility labels can help.
An interesting speech attribute for attributed accessibility labels is accessibilitySpeechIPANotation that lets you specify how VoiceOver should pronounce a label with the International Phonetic Alphabet (IPA) notation. https://developer.apple.com/documentation/foundation/nsattributedstring/key/accessibilityspeechipanotation
Guidelines from Apple: Begin with a verb that explains the results of the action. Avoid using the imperative form of a verb because that can make it sound like a command. Don’t include the action type. Don’t include the control. https://developer.apple.com/documentation/objectivec/nsobject-swift.class/accessibilityhint
