The content displayed on the screen should be confined to a specific orientation of the screen. Users may want to restrict the orientation of their device either to portrait or landscape due to various reasons. If the user decides to restrict the orientation of their device say to portrait, the content that is displayed only in landscape will never be available for these users.
For certain activities display of screen orientation to a specific mode is required for a best experience. For instance to capture a bank check, display a piano application landscape orientation may be best.
How to avoid fixed orientation
Android:
In Android screen orientation can be specified for an activity. By default, the screen orientation is unspecified. So to ensure that the screen orientation is not specific to any orientation do not specify the orientation to portrait, landscape or any other orientation values specified in the technology.
Eg: Android:screenorientation=”portrait” is not an accessible technique.
IOS:
No documentation found to lock orientation. However ensure that the orientation changes do not change the content or functionality of the screen.
WCAG Success Criteria
1.3.4 Orientation Level AA) WCAG 2.1 SC