There are a variety of questionnaire form options people use, such as Google Forms or and Qualtrics. The three main aspects to accessible form questionnaires;
- technical code behind the scenes,
- the actual content of the questions,
- and the visual design.
Optional form widgets are available for text, multiple-choice, and more. Some of these form widgets are more accessible than others. Below are links to some resources that explain which widgets have the potential to be accessible.
- List of accessible Qualitrics widgets
- List of accessible alternative Qualtics widgets
- How to check Qualtircs form for accessibility issues
It is possible to use an accessible widget, but ask a question in a way that does not make sense. An example would be, "Rate your opinion on a scale of 1 to 5". The problem with this is that there are no instructions indicating which is best. It is 1 best or is 5 best.
All other WCAG rules apply, like ensuring links have descriptive names.
More info on accessible form content.
Most questionnaires provide the option of choosing theme colors. Choose a theme that has easy to read text with a high contrast ratio.