WCAG 2.1
WCAG 2.1 is the W3C accessibility standard published June 2018 that adds 17 success criteria to WCAG 2.0, focused on mobile, low-vision, and cognitive needs. It is the operative legal target referenced by the ADA and the EAA at Level AA.
Detailed explanation
WCAG 2.1 introduced 17 new success criteria beyond WCAG 2.0, addressing gaps that emerged with the rise of mobile and touch interfaces. Notable additions at Level AA include 1.3.4 Orientation, 1.3.5 Identify Input Purpose, 1.4.10 Reflow, 1.4.11 Non-text Contrast, 1.4.12 Text Spacing, 1.4.13 Content on Hover or Focus, 2.5.1 Pointer Gestures, 2.5.2 Pointer Cancellation, 2.5.3 Label in Name, and 2.5.4 Motion Actuation.
WCAG 2.1 is fully backwards compatible with 2.0 — anything that conforms to 2.1 also conforms to 2.0. United States courts (Robles v Domino's, Gil v Winn-Dixie) cite WCAG 2.1 AA as the de-facto standard for ADA Title III compliance, even though no federal regulation explicitly mandates it for non-government commerce.
How this applies to Shopify stores
Shopify's Online Store 2.0 themes are built against WCAG 2.1 AA. AccessComply scans every Shopify storefront against the full 50-criterion 2.1 AA set — including the touch and reflow rules that desktop-only audits routinely miss.
Primary source: w3.org