# Back to Top ## What it is A floating button that appears in the bottom-right corner after you scroll past 500 pixels. Click it to smooth-scroll back to the top of the page. ## When to use it The back-to-top button is always on. It gives readers a quick way to return to the top of a long article without manually scrolling or using the sidebar. ## How it works `initBackToTop()` creates a `` (if one doesn't already exist in the markup) with an `aria-label` from config. The scroll handler in `initScrollBehavior()` toggles `.void-back-to-top--visible` when `scrollY > threshold` (default 500px). Clicking the button calls `window.scrollTo({ top: 0, behavior: "smooth" })`. ## Configuration ```yaml theme: void: content: show_back_to_top: true # Show the button (default true) back_to_top_label: "Back to top" # aria-label text back_to_top_threshold: 500 # Scroll distance in px before showing (default 500) ``` ## Under the hood - **File:** `void.js` — `initBackToTop()` (line ~1102), visibility toggled inside `initScrollBehavior.onScroll` (line ~1083) - **Element:** `.void-back-to-top` — created dynamically if not in markup - **Visibility:** `.void-back-to-top--visible` toggled when `scrollY > threshold` - **Config gate:** `componentShow("content", "show_back_to_top")` — absent defaults to on - **Threshold:** `content.back_to_top_threshold` (default 500) ## Accessibility notes - The button is a real `` with an `aria-label` — screen readers announce it as "Back to top". - Focus is not moved after clicking — the user stays in the document flow. - `prefers-reduced-motion: reduce` disables the smooth scroll animation.