What is overlay?

An overlay is a layer of visual or functional content that sits on top of another screen, image, or interface without permanently changing what’s underneath. Think of it like a transparent sheet you place over a picture to add extra information, buttons, or effects while still being able to see the original picture underneath.

Let's break it down

  • Base layer: the original content (a webpage, video, map, etc.).
  • Overlay layer: the extra content that appears on top (pop‑up window, tooltip, semi‑transparent color, etc.).
  • Transparency: overlays often have some see‑through quality so you can still recognize the base layer.
  • Interaction: you can usually click, tap, or close the overlay, and it can appear or disappear based on user actions.

Why does it matter?

Overlays let designers add helpful information or interactive elements without navigating away from the current view. This keeps users focused, reduces page loads, and creates smoother experiences-like showing a quick help tip while you’re filling out a form.

Where is it used?

  • Websites: modal dialogs, cookie notices, image lightboxes.
  • Mobile apps: in‑app tutorials, floating action buttons, temporary menus.
  • Video games: HUD (heads‑up display) showing health, ammo, or maps.
  • Video streaming: subtitles, captions, or interactive ads over the video.
  • Mapping services: pins, route details, or traffic alerts over a map.

Good things about it

  • Improves usability by providing context without leaving the page.
  • Saves bandwidth because you don’t need to load a whole new page.
  • Can be styled to match the brand while staying unobtrusive.
  • Enables quick interactions like confirming actions or displaying alerts.
  • Enhances visual appeal with animations and smooth transitions.

Not-so-good things

  • Overuse can annoy users, especially if overlays pop up too often.
  • Poorly designed overlays may block important content, causing frustration.
  • Accessibility issues arise if they aren’t keyboard‑navigable or screen‑reader friendly.
  • Large or heavy overlays can slow down page performance on slower devices.
  • If not dismissed properly, they can trap users, making it hard to return to the main content.