Compatibility with assistive technology (AT) such as screen readers is a precondition for universal design of ICT. This is also a requirement in the W3C WCAG guidelines. Experience shows that providing compatibility with one screen reader does not necessarily ensure compatibility with other screen readers from different vendors. It is therefore necessary to test an ICT solution with different AT from different vendors to ensure accessibility for all AT users. In this work, we investigate compatibility challenges with AT in depth and explore the potential for an online tool for AT compatibility testing.