Making sure that your website or application is accessible to all types of users (like the vision, hearing, cognitive, literacy, and the physically impaired) makes room for argument as this maybe the most underutilized methodology that exists today in user experience.
The Human Judgment
Most of accessibility testing involves our human judgment of how we would like to test the website or the application. This judgment comes from our testing and analysis adopted.
We need to strive forward and now make room for people who deserve to use software.
The Web Accessibility Initiative (WAI) of the World Wide Web Consortium (W3C) allows you to follow some guidelines that will help you in every step of your testing process. And if you do have the budget, invest in a tools called AccVerify, Bobby, or InFocus that will help you achieve this.
Looking for something free to begin with? Your best option is A Prompt.