HTML-to-app glossary

A

AAB (Android App Bundle)

The publishing format Google Play requires for new apps since 2021. An AAB cannot be installed directly; Play generates an optimised APK for each device from it. Learn more →

Adaptive icon

Android's launcher-icon format with a separate foreground and background layer, which the launcher crops to a circle, squircle or square. Keep your logo inside the central 66% of the canvas.

ADB

Android Debug Bridge — a command-line tool for installing apps and reading logs over USB. Not needed to install an APK you built; tapping the file is enough.

APK

Android Package — the file format Android installs. A ZIP containing compiled code, resources, assets, a manifest and a signature. Learn more →

appassets.androidplatform.net

A hostname Android reserves for apps to serve their own bundled files over https through WebViewAssetLoader. HTML apps built with HTML to App load from https://appassets.androidplatform.net/web/. Learn more →

Asset

A file packed into the APK's assets/ folder unchanged — your HTML, CSS, JS, images and fonts in an HTML app.

C

Capacitor

An open-source framework by Ionic that wraps web code in a native project and gives JavaScript access to native plugins. Learn more →

CDN

Content delivery network — a server that hosts libraries, fonts and media. Files loaded from a CDN need a connection inside an app. Learn more →

Closed testing

A Play Console release track for invited testers. New personal developer accounts must run a closed test with at least 12 testers for 14 days before production. Learn more →

Cordova

Apache Cordova, the original framework for packaging web apps with native plugins. Most new projects now use Capacitor. Learn more →

CORS

Cross-Origin Resource Sharing — server headers that allow a page on one origin to call an API on another. An HTML app's API must allow https://appassets.androidplatform.net.

D

Data safety form

The Play Console declaration of what data an app collects and shares, including data collected by its web pages, SDKs and APIs. Learn more →

E

Edge-to-edge

Drawing app content behind the status and navigation bars, the default on recent Android versions. Web pages handle it with viewport-fit=cover and safe-area insets. Learn more →

H

Hash routing

Single-page-app routing that keeps the route after the # in the URL (index.html#/settings). Required inside an APK, which has no server to rewrite paths. Learn more →

HTML 2 APK builder

A tool that converts HTML, CSS and JavaScript into an installable Android APK without code, by generating, compiling and signing a WebView app around the files. Learn more →

HTML5 game

A game built with web technologies — canvas, WebGL, Web Audio — typically with an engine such as Phaser, PixiJS or Construct. Packages into an APK unchanged. Learn more →

I

IndexedDB

The browser's built-in database for structured data and files; holds hundreds of megabytes and persists in an app across launches and updates. Learn more →

K

Keystore

A file (.jks or .keystore) that stores signing keys, each under an alias and protected by passwords. Learn more →

L

localStorage

Simple key-value browser storage of about 5 MB of strings, persistent inside an app. Learn more →

M

Minimum functionality

Google Play's policy that an app must offer a useful, app-like experience — not just a website in a frame. Learn more →

O

OneSignal

A push-notification service. HTML to App Pro uses it to deliver native push to HTML apps. Learn more →

P

Package name

The app's unique ID, such as com.yourname.app. It cannot be changed after publishing on Google Play.

Play App Signing

Google Play holding the app signing key and re-signing your uploads, so a lost upload key can be reset. Learn more →

PWA

Progressive Web App — a website with a manifest and service worker that browsers can install. Can be packaged into an APK for Google Play. Learn more →

S

Safe area

The part of the screen not covered by camera cut-outs, rounded corners or system bars; exposed to CSS as env(safe-area-inset-*). Learn more →

Service worker

A script that intercepts a website's network requests, used by PWAs for offline caching. Redundant in a bundled app, where files are already local. Learn more →

Sideloading

Installing an APK from a file rather than from an app store. Learn more →

Signing key

The private key whose signature proves an APK's origin. Every update of an app must be signed with the same key. Learn more →

Splash screen

The screen shown while an app starts. In an HTML app it covers the moment the WebView initialises. Learn more →

T

Target API level

The Android version an app declares it was built for (targetSdkVersion). Google Play raises the minimum every year. Learn more →

TWA (Trusted Web Activity)

A way to open a PWA full-screen in Chrome from an Android app. Requires a Digital Asset Links file on the website. Learn more →

U

Upload key

The key you sign AABs with before uploading to Google Play; distinct from the app signing key Google holds. Learn more →

V

Version code

An integer that must increase with every release of an app; Android uses it to decide what is an update.

Version name

The human-readable version (1.2.0) shown to users. It has no effect on updates.

Viewport meta tag

The tag that tells a mobile browser or WebView to lay a page out at device width. Essential in every HTML app. Learn more →

W

WebAssembly

A compact binary format that runs at near-native speed in browsers and in Android WebView; used by many game engines.

WebView

Android's component for showing web content inside an app, powered by the Chromium-based Android System WebView, updated through Google Play. Learn more →

WebViewAssetLoader

An AndroidX class that serves an app's bundled files over an https origin instead of file://, so modern web features work. Learn more →

Z

ZIP

The archive format used to upload a multi-file web project. index.html should be at the root of the archive. Learn more →