Three conformance levels exist and only one matters in practice. Level A covers the most severe barriers and is not sufficient on its own. Level AA is the working standard: it is what the Department of Justice cited in its rule for public entities, what the European Accessibility Act aligns with, and what plaintiffs point to in the accessibility lawsuits filed against private businesses every year. Level AAA includes requirements that are impossible to meet across an entire site and the guidelines themselves say it is not intended as a site wide target. Aim at AA and ignore the other two.
Version numbers cause confusion because there are several in circulation. WCAG 2.0 dates from 2008, 2.1 added criteria for mobile and low vision users in 2018, and 2.2 arrived in 2023 with a handful more. Most regulatory language still names 2.1 Level AA, which is the sensible target, and building to 2.2 costs almost nothing extra because it is additive rather than a replacement. If somebody quotes you a price to reach a specific version, the difference in work between 2.1 and 2.2 for a small business site is small.
What AA actually requires for a typical business site is less exotic than it sounds. Every image needs a text alternative or an explicit marker that it is decorative. Text needs sufficient contrast against its background. Everything must work by keyboard alone, without a mouse, including menus and forms. Form fields need labels that are programmatically connected rather than just visually adjacent. Headings need to describe the actual structure of the page. Video needs captions. Nothing may rely on color alone to convey meaning. And the page must remain usable when text is enlarged.
Test with automated tools first and understand their limit. Free scanners will find missing alternative text, contrast failures, and unlabeled fields in seconds, and that is genuinely valuable because those are the most commonly cited failures. But automated testing catches roughly a third of the criteria, because the rest require judgment about whether something makes sense. The manual tests worth doing yourself take about twenty minutes: unplug your mouse and try to complete your contact form using only the keyboard, then enlarge the text to two hundred percent and see whether anything becomes unusable.