Many individuals with severe motor impairments rely on Assistive Technologies (ATs) or Brain-Computer Interfaces (BCIs) to interact with digital devices such as their computers. Clinicians and researchers currently lack a common framework to objectively quantify how much a given AT or BCI improves real-world function or to compare across tools. This project seeks to address this gap by developing a standardized method to objectively assess or compare the functional benefit of these tools on digital independence, i.e., the ability to independently operate computers, phones, and other digital systems, by creating a unique Digital Assessment Interface (DAI). This assessment will be a simulation of online and digital activities that prior work has determined is important to functional daily living in the digital domain. Participants will complete this assessment with various ATs and BCIs, and these scores will be used to create an index, which will be comprised of performance outcomes, clinician-reported outcomes, and patient-reported outcomes. The tool aims to quantify and compare digital task performance across devices and user populations. The primary objective of this study is to develop an index. The index will quantify functional performance of individuals using various ATs and BCIs. The secondary objectives are to extensively evaluate the psychometric properties of the index, such as the validity, responsiveness, reliability, and floor/ceiling effects both globally and across different devices and impairment levels, ensuring that it can reliably measure the impact of an AT or BCI on a user's ability to independently operate digital systems; and to characterize the familiarization and use of specific BCI and AT systems with reference to a normative healthy control population.