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CSS
#rrggbbaa hex color notation
::first-letter CSS pseudo-element selector
::placeholder CSS pseudo-element
::selection CSS pseudo-element
:default CSS pseudo-class
:dir() CSS pseudo-class
:focus-within CSS pseudo-class
:has() CSS relational pseudo-class
:in-range and :out-of-range CSS pseudo-classes
:indeterminate CSS pseudo-class
:matches() CSS pseudo-class
:optional CSS pseudo-class
:placeholder-shown CSS pseudo-class
Blending of HTML/SVG elements
CSS @apply rule
CSS Appearance
CSS Canvas Drawings
CSS Containment
CSS Cross-Fade Function
CSS Device Adaptation
CSS Exclusions Level 1
CSS Grid Layout
CSS Initial Letter
CSS Masks
CSS Motion Path
CSS Reflections
CSS Scroll snap points
CSS all property
CSS background-attachment
CSS background-blend-mode
CSS currentColor value
CSS display: contents
CSS font-rendering controls
CSS font-size-adjust
CSS font-stretch
CSS hanging-punctuation
CSS image-set
CSS initial value
CSS line-clamp
CSS namespaces
CSS page-break properties
CSS position:fixed
CSS position:sticky
CSS revert value
CSS scrollbar styling
CSS text-indent
CSS text-justify
CSS text-orientation
CSS text-stroke and text-fill
CSS touch-action property
CSS unset value
CSS user-select: none
CSS widows & orphans
CSS will-change property
CSS writing-mode property
CSS zoom
CSS3 attr() function
CSSOM Scroll-behavior
Case-insensitive CSS attribute selectors
Explicit descendant combinator >>
Improved kerning pairs & ligatures
Media Queries: interaction media features
Rebeccapurple color
background-position-x & background-position-y
letter-spacing CSS property
selector list argument of :not()
selector list argument of :nth-child and :nth-last-child CSS pseudo-classes
CSS2
CSS 2.1 selectors
CSS Counters
CSS Table display
CSS inline-block
CSS min/max-width/height
display: flow-root
CSS3
@font-face Web fonts
CSS ::marker pseudo-element
CSS Animation
CSS Backdrop Filter
CSS Counter Styles
CSS Feature Queries
CSS Filter Effects
CSS Generated content for pseudo-elements
CSS Gradients
CSS Hyphenation
CSS Logical Properties
CSS Regions
CSS Repeating Gradients
CSS Shapes Level 1
CSS Variables (Custom Properties)
CSS background-position edge offsets
CSS background-repeat round and space
CSS box-decoration-break
CSS clip-path property (for HTML)
CSS element() function
CSS filter() function
CSS first-line pseudo-element
CSS font-feature-settings
CSS font-smooth
CSS font-variant-alternates
CSS outline properties
CSS overflow-anchor (Scroll Anchoring)
CSS pointer-events (for HTML)
CSS resize property
CSS text-size-adjust
CSS3 2D Transforms
CSS3 3D Transforms
CSS3 Background-image options
CSS3 Border images
CSS3 Border-radius (rounded corners)
CSS3 Box-shadow
CSS3 Box-sizing
CSS3 Colors
CSS3 Cursors (original values)
CSS3 Cursors: zoom-in & zoom-out
CSS3 Media Queries
CSS3 Multiple backgrounds
CSS3 Multiple column layout
CSS3 Opacity
CSS3 Overflow-wrap
CSS3 Text-overflow
CSS3 Text-shadow
CSS3 Transitions
CSS3 font-kerning
CSS3 image-orientation
CSS3 object-fit/object-position
CSS3 selectors
CSS3 tab-size
CSS3 text-align-last
CSS3 word-break
Crisp edges/pixelated images
Flexible Box Layout Module
Font unicode-range subsetting
Intrinsic & Extrinsic Sizing
Media Queries: resolution feature
TTF/OTF - TrueType and OpenType font support
Viewport units: vw, vh, vmin, vmax
calc() as CSS unit value
ch (character) unit
rem (root em) units
text-decoration styling
text-emphasis styling
Canvas
HTML5
Attributes for form submission
Audio Tracks
Audio element
Autofocus attribute
Canvas (basic support)
Color input type
Custom Elements v0
Custom Elements v1
Custom protocol handling
Datalist element
Date and time input types
Details & Summary elements
Dialog element
Download attribute
Drag and Drop
Email, telephone & URL input types
Form attribute
Form validation
HTML Imports
HTML Media Capture
HTML templates
HTML5 form features
Minimum length attribute for input fields
Multiple file selection
New semantic elements
Number input type
Offline web applications
PNG favicons
Pattern attribute for input fields
Picture element
Ping attribute
Range input type
Reversed attribute of ordered lists
Ruby annotation
Scoped CSS
Search input type
Session history management
Spellcheck attribute
Srcset and sizes attributes
Text API for Canvas
Toolbar/context menu
Video Tracks
Video element
Web App Manifest
accept attribute for file input
async attribute for external scripts
classList (DOMTokenList)
contenteditable attribute (basic support)
dataset & data-* attributes
defer attribute for external scripts
disabled attribute of the fieldset element
getElementsByClassName
hidden attribute
indeterminate checkbox
input event
input placeholder attribute
inputmode attribute
meter element
naturalWidth & naturalHeight image properties
progress element
readonly attribute of input and textarea elements
relList (DOMTokenList)
seamless attribute for iframes
srcdoc attribute for iframes
tabindex global attribute
wbr (word break opportunity) element
JS
JS API
Ambient Light API
Base64 encoding and decoding
Basic console logging functions
Battery Status API
Beacon API
Blob URLs
Blob constructing
BroadcastChannel
CSS Font Loading
CSS.supports() API
Channel messaging
Clipboard API
Cross-document messaging
CustomEvent
DOM Parsing and Serialization
DeviceOrientation & DeviceMotion events
Document Object Model Range
Document.execCommand()
Efficient Script Yielding: setImmediate()
Element.getBoundingClientRect()
Element.insertAdjacentHTML()
Element.scrollIntoViewIfNeeded()
Fetch
File API
FileReader API
FileReaderSync
Filesystem & FileWriter API
Full Screen API
Gamepad API
Geolocation
Hashchange event
High Resolution Time API
IndexedDB
Input Method Editor API
Internationalization API
IntersectionObserver
Media Source Extensions
MediaRecorder API
Mutation Observer
Navigation Timing API
Network Information API
Object RTC (ORTC) API for WebRTC
Online/offline status
Page Visibility
PageTransitionEvent
Payment Request API
Pointer events
PointerLock API
Printing Events
Promises
Proximity API
Push API
Resource Timing
Screen Orientation
Selection API
Server-sent events
Service Workers
Shared Web Workers
Speech Recognition API
Speech Synthesis API
TextEncoder & TextDecoder
Touch events
URL API
URLSearchParams
User Timing API
Vibration API
Web Animations API
Web Audio API
Web Bluetooth
Web MIDI API
Web Notifications
Web SQL Database
Web Sockets
Web Storage - name/value pairs
Web Workers
WebRTC Peer-to-peer connections
WebVR API
XMLHttpRequest advanced features
document.currentScript
document.evaluate & XPath
getComputedStyle
getUserMedia/Stream API
matchMedia
matches() DOM method
maxlength attribute for input and textarea elements
navigator.hardwareConcurrency
requestAnimationFrame
requestIdleCallback
scrollIntoView
PNG
Other
AAC audio file format
Brotli Accept-Encoding/Content-Encoding
CSS Paged Media (@page)
Data URIs
EOT - Embedded OpenType fonts
FLAC audio format
HEVC/H.265 video format
HTTP Live Streaming (HLS)
HTTP/2 protocol
JPEG 2000 image format
JPEG XR image format
MP3 audio format
MPEG-4/H.264 video format
MathML
Ogg Vorbis audio format
Ogg/Theora video format
Opus
SDCH Accept-Encoding/Content-Encoding
SPDY protocol
WAI-ARIA Accessibility features
WOFF - Web Open Font Format
WOFF 2.0 - Web Open Font Format
Wav audio format
WebAssembly
WebM video format
WebP image format
WebVTT - Web Video Text Tracks
XHTML served as application/xhtml+xml
XHTML+SMIL animation
asm.js
DOM
"once" event listener option
ChildNode.remove()
Client Hints: DPR, Width, Viewport-Width
DOM manipulation convenience methods
DOMContentLoaded
DOMMatrix
Element.closest()
Element.insertAdjacentElement() & Element.insertAdjacentText()
EventTarget.addEventListener()
EventTarget.dispatchEvent
KeyboardEvent.charCode
KeyboardEvent.code
KeyboardEvent.getModifierState()
KeyboardEvent.key
KeyboardEvent.location
KeyboardEvent.which
Mutation events
Node.compareDocumentPosition()
Node.innerText
Node.textContent
Passive event listeners
Resource Hints: Lazyload
Resource Hints: dns-prefetch
Resource Hints: preconnect
Resource Hints: prefetch
Resource Hints: preload
Resource Hints: prerender
Shadow DOM v0
Shadow DOM v1
Window.devicePixelRatio
autocomplete attribute: on & off values
document.elementFromPoint()
document.head
focusin & focusout events
querySelector/querySelectorAll
Security
'SameSite' cookie attribute
ChaCha20-Poly1305 cipher suites for TLS
Content Security Policy 1.0
Content Security Policy Level 2
Credential Management API
Cross-Origin Resource Sharing
Encrypted Media Extensions
FIDO U2F API
Link type "noreferrer"
Permissions API
Public Key Pinning
Referrer Policy
Server Name Indication
Strict Transport Security
Subresource Integrity
TLS 1.1
TLS 1.2
TLS 1.3
Upgrade Insecure Requests
Web Cryptography
X-Frame-Options HTTP header
crypto.getRandomValues()
rel=noopener
sandbox attribute for iframes