Rather than reading the visual page, a screen reader queries the browser’s accessibility tree, so how well a site works depends heavily on correct semantic HTML and ARIA rather than visual design. Users navigate with dedicated keyboard shortcuts to jump between headings, links, form fields, and landmark regions, often moving much faster through a well-structured page than a sighted user scrolling with a mouse.
The major screen readers are JAWS and NVDA on Windows, VoiceOver on Mac and iOS, and TalkBack on Android, and testing with at least one real screen reader is considered essential; automated scanners alone cannot catch everything a real screen reader user would encounter.