PDF accessibility ensures that documents can be consumed by assistive technologies such as screen readers, magnifiers, and braille displays. The checker validates documents against the PDF/UA (ISO 14289) standard and WCAG 2.1 guidelines.
Tag structure analysis verifies that all content is properly tagged with semantic elements. Headings must follow a logical hierarchy, lists must use list tags, and tables must include header cell designations and scope attributes.
Reading order verification checks that the logical order of content matches the visual layout. This is particularly important for multi-column layouts, sidebars, and documents with floating elements that may appear in unexpected positions in the tag tree.
Alternative text checking ensures that all images, charts, and decorative elements have appropriate alternative text descriptions or are marked as artifacts. The checker flags images without alt text and images where the alt text appears to be a filename rather than a meaningful description.
Color contrast analysis evaluates text against its background to ensure sufficient contrast ratios. The tool reports specific instances where contrast falls below the minimum thresholds specified in WCAG 2.1 Level AA guidelines.