---
type: explanation
---

# Mobile

**Free across all tiers.** Mobile uses the same [widget](widget.md) inside a WebView. There is no native PoW reimplementation; Cap stays in the WebView. See [ADR-0005](adr/0005-webview-only-mobile.md).

## The pattern

The customer's iOS / Android app embeds a WebView pointing at a small mobile-optimized embed page hosted on the Caputchin CDN. The user solves; the page bridges the resulting wrapped token back to the native app via the WebView's JavaScript bridge; the native app sends it to the customer's backend, which calls [`/siteverify`](api.md#post-siteverify-customer-backend--platform) like any web request.

```mermaid
sequenceDiagram
  participant App as Native app (iOS/Android)
  participant WV as WebView (Caputchin embed page)
  participant FC as Caputchin platform
  participant CB as Customer backend

  App->>WV: open https://embed.caputchin.com/?sitekey=...&game=...
  WV->>FC: widget loads, Cap challenge, game runs
  FC-->>WV: wrappedToken
  WV-->>App: postMessage / JS bridge: token
  App->>CB: API call carrying token
  CB->>FC: POST /siteverify with secret
  FC-->>CB: verification result
```

## What ships at MVP

- **The WebView pattern, documented.** See the [mobile-webview guide](guides/mobile-webview.md).
- **A mobile-optimized embed page** on the Caputchin CDN — same widget, mobile-friendly defaults (full viewport, touch-tuned). The widget's sandboxed game iframe is supported across the iOS WKWebView and Android System WebView versions in the project's support matrix; `srcdoc` + `sandbox="allow-scripts"` produces an opaque-origin document on both. See [ADR-0015](adr/0015-sandbox-game-iframe.md).

## What's deferred

- **Thin native SDKs (Swift / Kotlin).** Convenience wrappers around the same WebView. Will be free when they ship — they're DX sugar, not new capability. Built when customer demand emerges. Listed in [roadmap](roadmap.md#whats-deferred-entirely).
- **Native PoW.** Will not happen. Cap is a [dependency](principles.md#cap-is-a-dependency-not-a-foundation), and Cap runs in browsers.

## Why this posture

This matches Turnstile (WebView only, free) and Cap's own reality (browser-only PoW). Game authors don't write mobile-specific code; the same `register()` call powers both platforms. Customers pay nothing extra for mobile because there's nothing extra to maintain.