srcset
sizes
fetchpriority
blocking="render"
<model>
controlslist
Load certain resources only when needed.
<img src="picture.jpg" loading="lazy" /> <iframe src="supplementary.html" loading="lazy"></iframe>
Attributes that allow providing several source images with hints to help the browser pick the right one.
<img srcset="fairy-med.jpg 480w, fairy-large.jpg 800w" sizes="(max-width: 600px) 480px, 800px" src="fairy-large.jpg" alt="Elva dressed as a fairy" />
Begin work on certain resources early to improve performance. Syntax: <link rel="pre* | dns-prefetch | modulepreload">.
<link rel="pre* | dns-prefetch | modulepreload">
<link rel="preload" href="picture.jpg" /> <link rel="dns-prefetch" href="https://fonts.googleapis.com/" />
An added layer of security that helps to detect and mitigate XSS and other attacks.
Content-Security-Policy: default-src 'self'
Allows specifying a hint to help the browser prioritize fetching various resources.
<img src="logo.svg" fetchpriority="high" />
Specify that resources (scripts, stylesheets etc) should block rendering until loaded.
<script blocking="render" async src="async-script.js"></script>
Allows embedding 3D graphical content into HTML.
<model src="3d-assets/car"></model>
Prevent certain controls from appearing in the toolbar of a media element.
<video src="fun.mp4" controlslist="nodownload"></video>
<math>
<canvas>
<picture>
<svg>
<object>
<iframe>
<audio>
<video>
crossorigin
allow
referrerpolicy
sandbox
nonce
integrity
<time>
<data>
itemprop
itemscope
class="h-card"
class="h-event"
property
typeof
<script type="application/ld+json">
lang
dir
<ruby>
<rp>
<rt>
Intl.DateTimeFormat
Date.prototype.toLocaleString(lang, options)
Intl.Collator
String.prototype.localeCompare(lang, options)
Intl.ListFormat
Array.prototype.toLocaleString(lang, options)
Intl.NumberFormat
Number.prototype.toLocaleString(lang, options)
Intl.MessageFormat
Intl.PluralRules
Intl.RelativeTimeFormat
Intl.Segmenter
Intl.LocaleMatcher
Think of embedding (multimedia, iframes, SVG, etc), machine-readable data, internationalization & localization, security & privacy, performance etc. Missing features, browser incompatibilities, and other problems you face are all fair game.