Web API Compatibility Test

Introduction

This article is part of Browser Compatibility Test. Open the compatibility test tool to run WebGL, WebGPU, codec, and API probes in your current browser.

A web API compatibility test validates JavaScript API support, browser API availability, feature accessibility, and standards compliance across device, storage, and security categories.

Overview

Web API compatibility testing feature-detects the JavaScript APIs your application calls. Probes group device APIs, performance APIs, storage APIs, and security APIs, noting secure context and permission requirements for standards compliance.

A web API compatibility test validates JavaScript API support, browser API availability, feature accessibility, and standards compliance across device, storage, and security categories.

API validation distinguishes presence from permission state. navigator.mediaDevices may exist while camera permission is denied.

Device APIs including camera, microphone, geolocation, sensors, and USB require both API availability and user or policy consent.

Modern web applications call dozens of platform APIs across storage, networking, devices, and security. A structured API checklist prevents features from shipping globally when only a subset of browsers exposes the required objects.

Progressive web apps depend on overlapping APIs. When your roadmap includes install prompts or offline modes, continue with a progressive web app compatibility test after your baseline API matrix is green.

• ●JavaScript API support via typeof and in operator probes
• ●Browser API availability across device, storage, and security categories
• ●Feature accessibility with secure context and permission checks
• ●Standards compliance validation for modern platform APIs

Device, Storage, Performance, and Security APIs

Device APIs such as camera, microphone, geolocation, sensors, and USB require both API presence and appropriate permission state. Record prompt, granted, and denied separately from hard unsupported.

Storage APIs including Local Storage, IndexedDB, Cache API, and File System Access frequently require secure contexts. HTTP staging environments produce false failures that disappear once HTTPS is enabled.

Publish API results through a browser feature availability report so product and support teams can see which rows block release without reading raw probe code.

Key Formula

Distinguish API presence from permission state. Record prompt, granted, and denied separately from hard unsupported.

Version your API checklist when releases add dependencies. Diff probe lists in code review alongside feature flags.

Performance and Memory APIs help diagnose sluggish experiences, but they do not replace compatibility probes for API presence. Use both when investigating reported slowness on specific devices.

• ●Use consistent probe definitions across browsers
• ●Combine scores with qualitative failure notes
• ●Re-run after browser or driver updates

Step by Step

Apply these steps in order so compatibility results stay comparable across browsers and releases.

1. 1

   Inventory API calls

   Search your codebase for window, navigator, and document API usage.

2. 2

   Build probe functions

   One function per API with consistent return shape: supported, unsupported, or error.

3. 3

   Note secure context rules

   Flag APIs that require HTTPS so staging HTTP results are interpreted correctly.

4. 4

   Run in each browser

   Collect matrices for desktop and mobile targets including WebView shells.

5. 5

   Wire UI fallbacks

   Hide or replace controls when probes fail instead of showing broken features.

Practical Examples

A design tool needs Clipboard API write access. Probes fail on Firefox without permission. The UI keeps a visible copy manually button on failing browsers.

A mapping app checks geolocation and sensor APIs before enabling AR overlays. Missing sensor APIs route users to a static map view.

A collaboration tool gates screen capture behind getDisplayMedia probes. Browsers without the API still join calls, but recording buttons stay hidden with explanatory copy.

A fintech app requires WebAuthn for passwordless login. API probes on older enterprise browsers fail early, routing those users to traditional credentials instead of broken enroll flows.

• ●Save probe JSON with each support ticket
• ●Map failures to visible fallbacks
• ●Review examples in sprint retrospectives

FAQ

FAQShould I use polyfills instead of probes?

Polyfills help API shape gaps. Probes still tell you when behavior will be slow or incomplete.

FAQHow many APIs belong on a checklist?

Include APIs whose absence breaks core flows. Skip rare APIs until a feature needs them.

FAQCan I auto-generate the checklist?

Static analysis finds references, but runtime probes validate actual browser support.

FAQWhy do APIs pass in dev but fail for users?

Secure context, enterprise policy, private browsing, and extension blocks frequently differ between developer laptops and customer environments.

FAQHow do permissions affect API probes?

Presence probes confirm the API exists. Permission prompts require separate UX testing beyond basic compatibility checks.