CSS Opacity & Visibility

CSS Opacity & Visibility — Control element visibility with opacity, visibility, and display properties for fade effects and show/hide behavior. The guide walks through Opacity & Visibility. `opacity: 0` — fully transparent but still interacts (clicks, layout). `visibility: hidden` — hidden, still occupies space, doesn't interact. `display: none` — removed from layout entirely. `opacity: 0.5` — 50% transparent. Opacity animates smoothly with CSS transitions. `backdrop-filter: blur(4px)` — blur behind element (glass effect). The guide is organized into 1 sections that build on each other, each pairing a prose explanation with real CSS you can use as-is. Related guides: CSS Introduction, CSS Selectors, CSS Box Model, CSS Flexbox, CSS Grid. This is one of 68 CSS guides on CSS Reference — see the full list on the guides page. Look up any property mentioned in this guide from the search page or the CSS Reference homepage.