What it does
- Lets you add URLs and metadata for content that’s already available offline (within the scope of your current service worker).
- Enables the browser to potentially show those entries in a built-in UI for offline content.
- Also lets your web app query the index and present the same list to users inside your own interface.
How it fits into the platform
- ContentIndex.add() — register an offline page with metadata (title, description, icons, category, etc.).
- ContentIndex.getAll() — retrieve all indexed entries for display/management.
- ContentIndex.delete() — remove an entry by its id.
Important constraints and best practices
- Indexed entries don’t automatically expire. You should provide a way to clear saved items and/or periodically prune older entries.
- The API supports indexing URLs that correspond to HTML documents. You generally can’t index a media file URL directly (like an .mp4); instead, index an offline-capable page that presents that media.
- It’s marked experimental on MDN—check browser compatibility carefully before relying on it in production.
The contentdelete event
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Content Index API Demo</title>
<link href="style.css" rel="stylesheet" />
<script src="contentIndex_API.js" defer></script>
</head>
<body>
<h1>Content Index API Demo</h1>
<p>Status: <span id="status">Checking support...</span></p>
<!-- Demo Controls -->
<div id="controls" style="display:none;">
<button id="btn-add">1. Index Content (Add)</button>
<button id="btn-check">2. Check All Entries</button>
<button id="btn-remove">3. Un-Index Content (Remove)</button>
</div>
<!-- Logs for the demo video -->
<pre id="logs"></pre>
</body>
</html>
body {
font-family: sans-serif;
margin: 2em;
background-color: #f4f4f4;
color: #333;
}
#logs {
background: #f4f4f4;
padding: 10px;
margin-top: 20px;
}
// Standard cache setup
self.addEventListener('install', (event) => {
// In a real app, you MUST cache the URL you intend to index.
// The browser may refuse to index content if it detects it isn't cached.
const urlsToCache = [
'./',
'./index.html',
'./contentIndex_API.js',
'./article.html',
'./icon.svg'
];
event.waitUntil(
caches.open('demo-cache-v1').then((cache) => {
return cache.addAll(urlsToCache);
})
);
self.skipWaiting();
});
// 6. HANDLING SYSTEM DELETION
// This event fires if the USER deletes the content from the
// Browser/System UI (not from your web app's UI).
self.addEventListener('contentdelete', (event) => {
console.log(`Content deleted by user: ${event.id}`);
// Use this opportunity to clean up related cache data
event.waitUntil(
caches.open('demo-cache-v1').then((cache) => {
// Example: If the user deletes the index entry,
// we might want to remove the actual file from cache.
// return cache.delete('/article.html');
})
);
});
// HELPER: Simple logger for the demo
const log = (msg) => {
const logEl = document.getElementById('logs');
logEl.textContent += `> ${msg}\n`;
console.log(msg);
};
// 1. REGISTER SERVICE WORKER
const init = async () => {
if (!('serviceWorker' in navigator)) {
document.getElementById('status').textContent =
'Service Worker not supported.';
return;
}
try {
const registration = await navigator.serviceWorker.register('sw.js');
await navigator.serviceWorker.ready;
// 2. FEATURE DETECTION
if (!('index' in registration)) {
document.getElementById('status').textContent =
'Content Index API NOT supported in this browser.';
return;
}
document.getElementById('status').textContent = 'Ready. API Supported.';
document.getElementById('controls').style.display = 'block';
document.getElementById('btn-add').onclick = () => addToIndex(registration);
document.getElementById('btn-check').onclick = () =>
checkIndex(registration);
document.getElementById('btn-remove').onclick = () =>
removeFromIndex(registration);
} catch (error) {
console.error('SW Registration failed', error);
}
};
// 3. ADDING CONTENT TO THE INDEX
const addToIndex = async (registration) => {
try {
await registration.index.add({
// Unique ID for this item
id: 'article-123',
// The URL to launch. Must match the cached file.
url: './article.html',
// Display metadata
title: 'Offline Article Demo',
description:
'A sample article demonstrating offline content indexing capabilities.',
category: 'article',
icons: [
{
src: './icon.svg', // Points to local file
sizes: '128x128',
type: 'image/svg+xml' // Correct MIME type for SVG
}
]
});
log('Success: "article-123" added to Content Index.');
} catch (e) {
log(`Error adding to index: ${e.message}`);
}
};
// 4. RETRIEVING INDEXED CONTENT
const checkIndex = async (registration) => {
const entries = await registration.index.getAll();
log(`Current Index Count: ${entries.length}`);
for (const entry of entries) {
log(` - Found: ${entry.title} (ID: ${entry.id})`);
}
};
// 5. REMOVING CONTENT
const removeFromIndex = async (registration) => {
await registration.index.delete('article-123');
log('Success: "article-123" removed from Content Index.');
};
init();
