Per-URL TODO Chrome extension — single‑key capture, URL normalization, three sync paths

Knowledge workers — researchers, product managers, lawyers and developers — repeatedly lose micro-context when a quick action tied to a webpage is needed: bookmarks, copy-paste to a task app, or leaving noisy browser tabs are common workarounds that interrupt flow. At an addressable base of roughly 500M knowledge workers and a low-cost-add-ons market of about $6.0B (assuming $12 ARPU/year), that fragmented, per‑URL task pain is a meaningful, solvable niche. You could build a Per‑URL TODO Chrome extension that captures a task with a single keystroke, normalizes URLs to prevent duplicate or conflicting entries, and offers three sync paths: encrypted local-only storage for privacy-minded users, optional personal cloud sync for cross-device continuity, and a team sync mode with SSO for enterprise customers. Complement the capture with client-side AI that suggests titles, extracts actionables and clusters related tasks without sending page content to servers, and keep the UI deliberately minimal (per‑URL lists plus a fast global search) to minimize habit change and friction. This market is attractive now because more work runs in the browser, micro‑SaaS buying patterns make $5–$20/year products viable, and privacy-preserving, on-device intelligence reduces compliance barriers. The idea’s strengths are instant capture, clear privacy positioning, and flexible sync that fits different user risk profiles; realistic challenges include extension maintenance across Chromium updates, Chrome Web Store policy and permissions scrutiny, and the user-conversion curve from free to paid — all of which are manageable but should be accounted for in go-to-market and engineering plans.