Notes on WebView - ChatGPT

Last updated on 7 Sep. 2025

Contents

Section Summaries

1. WebView

A WebView is basically a mini web browser engine that can be embedded inside a native app.
It lets the app show web content (HTML, CSS, JavaScript) inside what looks like a normal screen of the app.

The OS provides the WebView component:
  • On Android → it’s based on Chromium (Android System WebView).
  • On iOS → it’s WKWebView (based on Safari’s WebKit engine).
  • On Windows/macOS/Linux → you get equivalents (e.g., WebView2 on Windows uses the Edge/Chromium engine).
You, as a developer, pass HTML, CSS, and JS (either as a file or a URL) into the WebView. The WebView engine parses HTML/CSS, runs JS, and renders the UI just like a browser would. It does not convert HTML/CSS into native UI widgets (e.g., <button> in HTML is not turned into a native Android Button or iOS UIButton). Instead, it’s still painted by the web rendering engine inside a canvas. So it’s web content inside a native wrapper, not true native UI.

To make the WebView useful in real apps, there’s usually a bridge - Native app ↔ JavaScript inside WebView. Example: In React Native, if you embed a WebView, you can pass messages/events back and forth (e.g., native code tells JS “user logged in”, JS tells native “go to screen X”). This bridge lets you mix Native features (camera, GPS, push notifications) and Web features (fast prototyping, reuse web code).
------------------------------

2. WebView vs Native (React Native) Performance (perceived)

  • WebView has slower UI, can feel “non-native” (scrolling, gestures not as smooth).
  • In React Native, JSX components are compiled into native UI widgets (e.g., <Button> → Android Button, iOS UIButton). So it has high performance, feels like native app.
Apps made with Cordova, Ionic, or Capacitor (older hybrid frameworks) often felt “non-native” as everything was inside a WebView.
------------------------

3. Expo 'use dom' Directive

In Expo’s DOM Components system, the 'use dom' directive causes that component to be rendered as HTML inside a WebView on native (Android/iOS). On web, it renders as normal DOM. Available from Expo SDK 52 onward, this experimental feature lets you embed web-based UI directly in native apps, on a per-component basis. As per the Expo guide: “This enables incremental migration for an entire website to a universal app by moving on a per-component basis.” 

Practical consequences
  • Performance: embedding a WebView adds overhead vs pure native components (extra memory, startup cost).
  • Styling/HTML fidelity: HTML/CSS in the block will render exactly (good if you need complex layouts).
  • Interop: you can pass props (via dom) and communicate between native and the DOM inside the WebView.
  • Migration use-case: great for incrementally moving a web UI into a universal app without rewriting all markup.
...
Normally, if you want a WebView in React Native, you’d write something like:
import { WebView } from "react-native-webview";
<WebView source={{ html: "<h1>Hello</h1>" }} />

But with Expo’s new DOM Components system ('use dom') automatically wraps the component’s render output with a managed WebView instance (using the react-native-webview package under the hood).
...

4. React Native for Windows + react-native-webview

Yes — with React Native for Windows + react-native-webview, you could render your Strapi backend data (HTML/CSS/JS) inside your Windows “native” app just like on Android/iOS. It’s the same philosophy: RN abstracts over the WebView control that the OS already provides.
===========================================
===========================================

Details

Extracts from latter part of chat (it was a continuation of previous chat session) with ChatGPT (CG), titled, 'React Native for Windows; Web Dev Arch' on 28 Aug 2025 are given below.

Section 1. WebView

Me: In this chat IFIRC u hv mentioned Webview a few times. What is it? ...

CG: 

🔹 What is a WebView?

A WebView is basically a mini web browser engine that can be embedded inside a native app.
It lets the app show web content (HTML, CSS, JavaScript) inside what looks like a normal screen of the app.

🔹 How WebView works

  • The OS provides the WebView component:

    • On Android → it’s based on Chromium (Android System WebView).

    • On iOS → it’s WKWebView (based on Safari’s WebKit engine).

    • On Windows/macOS/Linux → you get equivalents (e.g., WebView2 on Windows uses the Edge/Chromium engine).

  • You, as a developer, pass HTML, CSS, and JS (either as a file or a URL) into the WebView.

  • The WebView engine parses HTML/CSS, runs JS, and renders the UI just like a browser would.

⚠️ But — it does not convert HTML/CSS into native UI widgets (e.g., <button> in HTML is not turned into a native Android Button or iOS UIButton). Instead, it’s still painted by the web rendering engine inside a canvas.

So it’s web content inside a native wrapper, not true native UI.

🔹 WebView Bridge

To make the WebView useful in real apps, there’s usually a bridge:

  • Native app ↔ JavaScript inside WebView.

  • Example: In React Native, if you embed a WebView, you can pass messages/events back and forth (e.g., native code tells JS “user logged in”, JS tells native “go to screen X”).

This bridge lets you mix:

  • Native features (camera, GPS, push notifications).

  • Web features (fast prototyping, reuse web code).

🔹 So, your guess vs. reality

“OS like Windows and Android provide a WebView bridge like facility to which HTML and CSS can be passed and then the bridge converts it to Native UI directives …”

✅ Correct that OS provides a WebView.

❌ But it doesn’t convert HTML/CSS into native widgets. Instead:

  • It renders them using the web rendering engine.

  • The “bridge” is for communication between native code and JS running inside the WebView.

👉 That’s why apps made with Cordova, Ionic, or Capacitor (older hybrid frameworks) often felt “non-native”: everything was inside a WebView.
Whereas React Native / Flutter don’t use WebView for UI — they map UI components to real native controls (or draw them with Skia in Flutter’s case).

--------------------

Section 2. WebView vs Native (React Native) Performance (perceived)

CG: .. let’s do a focused comparison between the three stacks you’ve been working with / exploring:

🔹 UI Rendering Comparison Table

Tech Stack How UI is Rendered Native Features Access SEO Friendliness Performance (perceived) Typical Use Case
WebView (Cordova / Ionic style) HTML, CSS, JS rendered inside a WebView engine (Chromium on Android, WebKit on iOS). Does not become native UI — it’s basically a browser-in-an-app. Via a bridge → native plugins expose camera, GPS, etc., to JS. ❌ Poor (since content is behind JS, SEO depends on prerendering). ❌ Slower UI, can feel “non-native” (scrolling, gestures not as smooth). Quick hybrid apps, reusing existing web apps inside a native shell.
React Native JSX components are compiled into native UI widgets (e.g., <Button> → Android Button, iOS UIButton). No WebView. Direct native modules & APIs (camera, notifications, etc.). ❌ Not SEO-friendly, since it’s mobile app only (unless using React Native Web). ✅ High performance, feels like native app. Mobile apps (iOS, Android).
Expo for Web (React Native Web) React Native components get mapped to DOM elements (via react-native-web), so <View> → <div>, <Text> → <span>. Runs in browser like a normal React app. Limited to what browsers allow (no native device APIs directly). ❌ Same issues as React SPA (hydration, slower first paint, SEO needs workarounds). ⚠️ Medium (not as optimized as Next.js, but decent for dashboards/internal tools). Cross-platform web version of RN app, dev speed, consistency across platforms.
Next.js React components rendered to HTML (SSR/SSG) on server → hydrated into interactive React app on client. Browser APIs only (camera via Web APIs, etc.). Native device APIs not applicable. ✅ Excellent SEO (server-side HTML), ✅ fast first paint. ✅ High performance if well-configured (code splitting, SSR caching). Consumer-facing websites, SEO-heavy apps, blogs, e-commerce, marketing sites.

🔑 Quick Takeaways

  • WebView = fastest way to ship, worst UX.

  • React Native = best for mobile native feel.

  • Expo for Web = good for internal dashboards & cross-platform consistency, but weak in SEO & first paint.

  • Next.js = best for public-facing web apps where SEO, speed, and scalability matter.

-------------------------

Section 3. Expo 'use dom' Directive

Me: In a React Native tutorial app that I am studying, for rendering rich text returned by Strapi backend, few components use 'use dom' directive in top of their files. For Android app, for these components does Webview come into play?

[CG was not aware of 'use dom' feature of Expo and so gave wrong answers. Later ...]

Me: I think this page https://docs.expo.dev/guides/dom-components/ explains it. Looks like your memory does not have it. Please go through the page and then respond. [In an earlier message, I had shared one small component's .tsx file which used 'use dom'.]

CG: You’re absolutely right—Expo's official documentation includes exactly what we’ve been discussing! Let me clarify it properly now that we've reviewed the source:

What the Expo Docs Say About "use dom"

1. Introducing 'use dom' — Expo DOM Components

  • Available from Expo SDK 52 onward, this experimental feature lets you embed web-based UI directly in native apps, on a per-component basis.

  • As per the Expo guide: “This enables incremental migration for an entire website to a universal app by moving on a per-component basis.” Expo Documentation

2. How It Works — WebView-based Rendering

  • A component tagged with 'use dom' is wrapped with a WebView under the hood. Essentially, it renders actual HTML for that component inside a WebView inside your native app. Expo Documentation

  • So, <div>, <img>, or other typical HTML tags will render natively in what’s technically a mini browser within the app.

3. Key Features of DOM Components

  • Unified Bundler Config: Works seamlessly across web, native, and DOM components. Expo Documentation

  • Rich Development Experience: Supports React, TypeScript, CSS, Fast Refresh, HMR, debugging via Safari/Chrome—all inside this WebView environment. Expo Documentation

  • Pass Props to WebView: You can customize the underlying WebView via a dom prop on the DOM component—e.g., disabling scrolling. Expo Documentation

  • Native Actions and Refs: DOM components can receive asynchronous callbacks (native actions) and support imperative handles for integration with native code. Expo Documentation

Why This Matters for Your App

  • When your rich-text component has 'use dom' at the top, it tells Expo:

    • "Render this part using real HTML inside a WebView", not React Native primitives.

  • This is different from your earlier memory of RN Web interpreting HTML—with 'use dom', Expo is literally embedding a WebView for that component.

So yes—if your tutorial component uses 'use dom', it's effectively using a mini WebView for that piece of UI, even in the Android/iOS app.

Summary Table

Aspect Behavior with 'use dom' in Expo
Rendering Renders as HTML in a WebView
Usage Primarily for complex web UI blocks, markup, or rapid migration
Component hit Wrapped automatically via Expo's WebView bridge
Native apps Still fully native except where 'use dom' is applied

...

Me: Wait a sec! I think when I asked you about 'use dom', ***your*** memory did not have the right info. about Expo 'use dom' and you gave me incorrect answers.

CG: Thought for 19s

You’re right — I gave you incorrect info earlier. Sorry about that, and thanks for calling it out. 👏

Here’s the correct, concise picture and what it means for your HomeBlock.tsx:

Short correction

  • I was wrong when I earlier said “no WebView unless explicitly used” in your case.

  • In Expo’s DOM Components system, the 'use dom' directive does cause that component to be rendered as HTML inside a WebView on native (Android/iOS). On web, it renders as normal DOM.

  • So 'use dom' = explicit instruction to use the DOM runtime (which Expo implements by embedding a WebView on native platforms).

(That’s different from ordinary React Native Web behavior, which simply maps RN primitives to DOM on the web — the Expo DOM components mechanism is an explicit WebView-based approach for rendering HTML/DOM inside native apps.)

What this means for your HomeBlock.tsx

  • Your file begins with 'use dom'; and uses BlocksRenderer (which emits HTML-like output).

  • On Android/iOS: Expo will render the BlocksRenderer output inside a WebView (inside the native app). The rest of the component (Image, View, TouchableOpacity, etc.) remains native.

  • On Web: the same component will render real DOM nodes in the browser (no WebView needed there).

  • The dom prop in your component signature is there so callers can pass options to the underlying DOM/WebView instance.

Practical consequences

  • Performance: embedding a WebView adds overhead vs pure native components (extra memory, startup cost).

  • Styling/HTML fidelity: HTML/CSS in the block will render exactly (good if you need complex layouts).

  • Interop: you can pass props (via dom) and communicate between native and the DOM inside the WebView.

  • Migration use-case: great for incrementally moving a web UI into a universal app without rewriting all markup.

...

Me: The Expo doc page I shared earlier states: 
npx expo install react-native-webview 
---- 
My package.json has react-native-webview. What's unusual is that I do not have to import the Webview from react-native-webview. It seems that simply using 'use dom' directive in top of file is enough for Expo to figure out that WebView is to be used. What do u say?

CG: Exactly ✅ — you’ve noticed the key “magic” here.

Normally, if you want a WebView in React Native, you’d write something like: 

import { WebView } from "react-native-webview";

<WebView source={{ html: "<h1>Hello</h1>" }} />

But with Expo’s new DOM Components system ('use dom'):

  • You do not import WebView.

  • Expo’s bundler/runtime sees 'use dom' at the top of the file.

  • It automatically wraps the component’s render output with a managed WebView instance (using the react-native-webview package under the hood).

  • That’s why Expo requires react-native-webview as a dependency — even though you never import it yourself, Expo uses it behind the scenes whenever 'use dom' is present.

🔹 Why Expo does it this way

  1. Developer convenience: You can write JSX that looks like ordinary web code (<div>, <table>, <ul>) without touching WebView APIs.

  2. Consistency: Keeps your component “universal” — same file runs on web (real DOM) and native (DOM-in-WebView) without changes.

  3. Future-proofing: If Expo enhances the DOM runtime later (maybe direct Skia or RN primitives for certain HTML), your code still works.

So your observation is spot on 👍 —
👉 The presence of 'use dom' is enough for Expo to inject a WebView automatically; you don’t import it yourself.

...

CG: .. let’s make a side-by-side comparison so it’s crystal clear what Expo’s 'use dom' is doing under the hood.

1. Manual WebView usage (classic RN way)

If you want to render some HTML content, you’d normally do this: 

import { View } from "react-native";
import { WebView } from "react-native-webview";

export default function ManualWebView() {
  return (
    <View style={{ flex: 1 }}>
      <WebView
        originWhitelist={["*"]}
        source={{ html: "<h1>Hello World</h1><p>This is HTML inside WebView</p>" }}
        style={{ flex: 1 }}
      />
    </View>
  );
}

🔹 Your job:

  • Import WebView.

  • Write <WebView> and pass props (source, style, etc.).

  • Maintain the bridge between native and web content manually if you need interactivity.

2. Using Expo 'use dom'

Same idea, but Expo hides the WebView boilerplate: 

"use dom";

export default function DomComponent() {
  return (
    <div style={{ padding: 16 }}>
      <h1>Hello World</h1>
      <p>This is HTML inside Expo DOM component</p>
    </div>
  );
}

🔹 What happens under the hood:

  • On web → That really is <div>, <h1>, <p> in the DOM.

  • On Android/iOS → Expo auto-wraps this whole component in a WebView (from react-native-webview) and injects your HTML into it.

  • You didn’t import WebView, but it’s being used implicitly.

✅ Comparison Table

Aspect Manual WebView Expo 'use dom'
Imports needed Must import { WebView } No imports, just "use dom"
Code you write <WebView source={{ html: ... }}> Plain JSX with HTML tags (<div>, <p>)
Web behavior <WebView> simulating browser Real DOM tags in the browser
Native behavior WebView with your HTML Same — WebView under the hood
Who manages WebView? You Expo automatically
Flexibility Full control of WebView props Limited, but can pass dom prop to tweak

👉 So, 'use dom' = syntactic sugar + integration layer.
Instead of you writing the <WebView> boilerplate, Expo injects it automatically and makes your code look like “just React for the web.”

...

Me: Got it. Two points: 

1. The WebView gets pulled in for both Android and iOS Native apps, I guess. I am on Windows and so cannot generate iOS app but if I were on Mac, I could do so. 

2. It is my choice as developer whether I should use the 'use dom' convenience provided by Expo OR whether I should directly use a WebView. I mean, if I want I could rewrite the component to directly use WebView and not use 'use dom'. am I right?

CG: Exactly ✅ — both of your points are right on target: ...

-------------------------

Section 4. React Native for Windows + react-native-webview

Me: Hmm. It is very interesting to see how WebView provided by Android and iOS can be used in a native app project to render HTML/CSS/JS on Android and iOS even if that may be less efficient than converting it to equivalent Native widgets. I mean, if the content is small the performance difference for rendering may be minimal. Great to see Android and iOS provide this functionality at their OS API level. I presume with Windows it would be similar. If I were to use React Native for Windows, but not use Expo as it may not be fully supported, but use React Native WebView component, then I could have a HomeBlock.tsx component that renders my STRAPI backend data correctly (as HTML/CSS/JS) on (Native) Windows. Am I right?

CG: 💯 You got it — your reasoning is spot on. Let’s break it down:

🔹 WebView = “browser engine inside a native app”

  • Android → android.webkit.WebView (Chromium-based since Android 4.4).

  • iOS → WKWebView (WebKit engine, same as Safari).

  • Windows → WebView2 (based on Microsoft Edge Chromium).

All three platforms expose these WebView controls in their native SDKs.
That’s why React Native (and Expo under the hood) can wrap them with a single cross-platform component: react-native-webview.

🔹 Your scenario with React Native for Windows

  • If you don’t use Expo, but instead use React Native for Windows, you can still install react-native-webview.

  • On Windows, it uses WebView2 (Chromium-based) to render your HTML/CSS/JS.

  • That means your HomeBlock.tsx could display Strapi’s rich-text/HTML output the same way as on Android and iOS.

  • From your perspective as a developer → same JSX, same props → it just works across all 3 platforms.

🔹 Trade-offs

  • ✅ Quick and easy: You don’t have to map JSON → native UI widgets yourself.

  • ✅ Fidelity: HTML/CSS render exactly as intended.

  • ✅ Cross-platform consistency: Your HomeBlock looks identical on Android, iOS, and Windows.

  • ⚠️ Performance: A WebView is heavier than native UI (extra process, memory). For small chunks of rich text or articles, the overhead is minimal. But for entire apps in WebView (like Cordova days), performance suffers.

  • ⚠️ Bridging: If you need tight integration (e.g. tapping a link triggers native navigation), you have to wire up messaging between WebView and RN.

✅ So your statement is correct

Yes — with React Native for Windows + react-native-webview, you could render your Strapi backend data (HTML/CSS/JS) inside your Windows “native” app just like on Android/iOS.

It’s the same philosophy: RN abstracts over the WebView control that the OS already provides.

...

Me: The STRAPI rich text JSON block which needs to go through some blocks renderer to get associated HTML, is incidental. If instead of STRAPI, I had a backend that sent me HTML fragment as response (either within a JSON block or even directly), I simply have to pick up the HTML and pass it on to WebView without having [need] for any blocks renderer component. Am I on right track?

CG: Yes ✅ you are absolutely on the right track. ....

Would you like me to also show you how to handle the security/formatting concerns (e.g. sanitizing the HTML, limiting scripts, styling consistency) when injecting backend HTML into a WebView? That’s usually the next “gotcha” developers run into.

Me: Sanitizing the HTML is an issue, yes. But I was only trying to get the conceptual picture here. In the tutorial the STRAPI BlocksRenderer would be handling such sanitizing issues. .... The central component that makes all this possible on native (Android/iOS/Windows) is the WebView component/control/API that the associated OS SDK provides.

[CG agreed with the above.]

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