This paper offers an overview of changes introduced in the recent Web Content Accessibility Guidelines (WCAG) 2.1 standard that have implications for the accessibility of content in science, technology, engineering and mathematics (STEM) disciplines. In reviewing new provisions of WCAG 2.1, interpretive questions are raised regarding their application to mathematical and scientific materials. The paper is concluded with a brief discussion of opportunities for further enhancing accessibility of STEM materials in future revisions of the Guidelines.