The Apis Not Covered Here

The web platform has hundreds of JavaScript APIs. This series covers 36 of them.

That sounds like a narrow slice. It is, and it is not.

The 36 covered here are the ones most developers have never used at all. The ones not covered are the ones you probably already know exist, even if you haven't used them deeply yet. The web capabilities overview covers the six areas this series focuses on.

The Capabilities This Series Skips

Here is the wider landscape, grouped by what they do.

Networking and Threading

Fetch API -- the modern interface for HTTP requests. The standard way to talk to a server, handle JSON responses, and manage headers. If you do not know this one yet, start here before anything else.

Web Workers -- JavaScript runs on a single thread. Web Workers let you offload heavy computation to a background thread so the UI doesn't freeze.

WebSockets -- a persistent two-way connection between your browser and a server. Used for real-time features like chat, live updates, and multiplayer.

WebRTC -- peer-to-peer communication directly between browsers. Video calls, screen sharing, file transfer without going through a server.

WebOTP -- reads a one-time password code from an incoming SMS automatically. When a user gets a verification code texted to them, this API can intercept it and pre-fill the form.

Storage and File Access

Covered fully in a dedicated course. The short version:

localStorage / sessionStorage -- simple key-value storage, synchronous, limited to about 5MB.

IndexedDB -- structured object storage in the browser. Transactional, async, no size limit worth worrying about for most apps.

Cache API -- part of the Service Worker stack. Stores request-response pairs for offline use.

File System Access API -- lets users grant a web app permission to read and write actual files on their filesystem. Not localStorage -- real files on disk.

UI and Graphics

Canvas API -- a 2D drawing surface for images, charts, and game graphics. Low-level, pixel-by-pixel control.

WebGL -- hardware-accelerated 3D graphics in the browser. Powers games, data visualizations, and 3D editors.

WebGPU -- direct access to the GPU for high-performance 3D content and compute workloads. More powerful than WebGL and designed for the modern GPU pipeline. Shipping in Chrome; still experimental in Firefox and Safari.

View Transitions API -- animates between page states or page navigations with CSS-driven transitions. Closes the visual gap between multi-page apps and native apps, which have always had smooth screen-to-screen animations.

EyeDropper API -- lets the user pick a color from anywhere on the screen using a native eyedropper tool. Chromium only.

Picture in Picture -- keeps a video playing in a floating overlay even when the user navigates away from the browser tab or switches apps. Available in all major browsers.

Screen Capture -- lets your app capture what is on screen. Used in web-based video conferencing to implement "share your screen."

Pointer Lock -- hides the cursor and gives you raw mouse movement data. Standard approach for first-person game controls.

Web Components -- a set of browser APIs for creating custom HTML elements with encapsulated styles and behavior. Not framework-specific.

Performance and Runtime

WebAssembly -- compile C, Rust, Kotlin, or other languages to a bytecode format that runs at near-native speed in the browser. Powers apps like Figma, AutoCAD web, and Google Earth.

Web Crypto -- cryptographic primitives in the browser. Hashing, signing, encrypting, generating keys. Nothing to do with blockchain.

Web Performance APIs -- PerformanceObserver, LCP, CLS, layout timing, and the full suite of browser performance instrumentation.

Compute Pressure API -- reports when the CPU is under high load so your app can reduce its workload. If the device is rendering an 8K video and your code is polling aggressively, the Compute Pressure API lets you know to back off.

Compression Streams -- zip and unzip binary data client-side using the native CompressionStream and DecompressionStream APIs. No library required. Available in all major browsers.

Web Transport -- a newer transport protocol for low-latency bidirectional communication with a server. Offers lower overhead than WebSockets for use cases like real-time games or live video processing.

Presentation API -- lets a web app send content to an external display, a Chromecast, or an Apple TV. Useful for slideshows and presentations from a browser.

Digital Goods API -- for PWAs published through the Play Store or App Store. Lets you charge users for subscriptions or in-app purchases using the store's payment infrastructure from within a PWA.

Network Information API -- tells you the connection type (Wi-Fi, 4G, offline) and estimated bandwidth. Useful for adaptive loading.

Device Memory API -- tells you how much RAM the device has. Useful for deciding how much data to prefetch or how aggressively to cache.

PWA and Background

Service Workers -- a script that runs independently of the page, in the background. Handles caching, offline fallback, and push notification delivery.

Web App Manifest -- a JSON file that turns a web app into an installable PWA with an icon on the home screen.

Background Sync -- lets a Service Worker retry failed network requests when connectivity is restored, even after the user has closed the page.

Background Fetch -- downloads large files in the background with progress tracking, even if the tab is closed.

Web Push -- sends notifications from your server to users' devices. Works even when the user is not on your site. Available on iOS since Safari 16.4, for installed PWAs only.

Page Visibility API -- fires an event when the user switches away from your tab or minimizes the browser. Useful for pausing video, stopping polling, or saving state.

Media Session API -- lets a background audio or video player appear in the device's media controls -- the lock screen, a car's CarPlay display, or an Apple Watch.

Authentication and Security

Web Authentication (WebAuthn) -- the API behind passkeys and passwordless login. Lets users authenticate with Face ID, Touch ID, or Windows Hello instead of a password.

Credential Management API -- stores and retrieves credentials client-side. Works with WebAuthn, federated login, and traditional username-password flows.

These two APIs together represent the direction the entire web authentication space is moving. Service Workers and PWA each warrant their own deep dives -- this series links to those when relevant.

Why They Are Not Here

None of these are unimportant. Most of them are important enough to warrant a full course on their own.

This series focuses on capabilities that most developers have never touched -- sensors, hardware connectivity, OS integration, speech, vision. The APIs above are either well-covered elsewhere or too deep to survey quickly.

The bridge to next is the permission model. Before any sensor, Bluetooth connection, or camera feed, the browser asks the user for permission. Understanding how that model works is the foundation for everything that follows.

The Essentials

1. The web platform has hundreds of APIs. This series covers 36 -- specifically the hardware and OS integration layer that most frontend developers have never reached for.
2. Storage, Service Workers, WebAuthn, WebRTC, and Canvas all have deep dedicated coverage elsewhere -- they are out of scope here, not unimportant.
3. The map is bigger than any single series can cover. Knowing what exists -- even the things you are not learning today -- is itself useful when a requirement arrives.