Module 09: SMS, Mobile, PWA

Anchor outcome PWA installed on 1,340 devices. Push notifications for price drops and new listings: 18% click-through rate (vs. 2% CTR for equivalent email). A2P 10DLC registered and in production — zero carrier rejections in 90 days.

62% of the Anchor site’s traffic was mobile at the time this module was built. Most of that traffic was a desktop site that happened to be viewable on a phone — small tap targets, no home screen install, no offline capability, and no way to reach those visitors again except email. This module closes all four of those gaps.

The 4 lessons

Lesson 9.1

PWA vs Native App Trade-offs

The decision framework for when PWA wins, the manifest.json that makes a site installable, display modes, iOS quirks (no automatic install prompt, limited push), and why one codebase beats two for dealer inventory.

Lesson 9.2

Service Worker Architecture

Registration, cache-first for static assets vs. network-first for pages, cache versioning with delete-on-activate, the offline fallback page, and serving sw.js with no-cache headers so version updates propagate.

Lesson 9.3

Push Notifications for Leads

VAPID key generation, push subscription storage indexed by endpoint hash, opt-in UX that precedes the browser permission dialog, server-side send for price drops and new listing alerts, and expired subscription cleanup.

Lesson 9.4

SMS Compliance Rail

TCPA express written consent at inquiry forms, consent stored with timestamp and source URL, STOP keyword handler that opts out in the same request cycle, and A2P 10DLC Brand + Campaign registration for zero carrier rejections.