How I Built an Accessibility Scanner That Checks 201 WCAG Criteria

Building web accessibility tools isn't just about checking boxes — it's about making the web usable for everyone. Here's how I approached building AccessiScan, a WCAG 2.1 accessibility scanner. The Problem Most accessibility scanners check only 30-50 common issues. That leaves hundreds of potential barriers undetected. I wanted something more comprehensive. Architecture Decisions Client-Side First The scanner runs primarily in the browser. This means: No data leaves the user's machine Instant feedback (no server round-trips) Works offline once loaded 201 Individual Checks Each WCAG criterion gets its own check function. They're organized by conformance level: Level A (78 checks): Essential requirements. Missing alt text, keyboard traps, missing form labels. Level AA (86 checks): Standard compliance. Color contrast, resize text, consistent navigation. Level AAA (37 checks): Enhanced accessibility. Sign language, extended audio descriptions. Scoring System Rather than a simple pass/fail,