Screen reader
A screen reader is assistive software that converts on-screen content into synthesized speech or refreshable braille, enabling blind and low-vision users to navigate websites, apps, and documents.
Detailed explanation
Screen readers translate the structure and content of a webpage into a linear, audible experience. They rely on the underlying HTML semantics — heading levels, list structure, link text, form labels, ARIA — not on visual styling.
The most-used screen readers are JAWS (commercial, Windows), NVDA (free, Windows), VoiceOver (built into macOS and iOS), and TalkBack (Android). Each has subtle differences in announcement behavior, but all rely on the same accessibility tree exposed by the browser.
Because screen readers read the source HTML, JavaScript overlays that "fix" accessibility at runtime do not help. The screen reader has already announced the broken markup before the overlay loads. Source-code fixes are the only durable answer.
How this applies to Shopify stores
On a Shopify storefront, a screen reader user navigates through your theme's heading structure, product list, and cart with keyboard shortcuts. If your theme has missing form labels, broken heading order, or unlabeled icon buttons, the screen reader user gets stuck. AccessComply audits every theme through the same accessibility tree the screen reader uses.
Primary source: webaim.org