AddThisFeature

Image Lightbox

Open images at a useful size without sending users to a raw file URL.

moderate UI & Polish

What it adds

An overlay viewer that shows an image at full size with zoom, keyboard control, and a clean way out.

What your agent is told to do

6
  1. 1

    Open the viewer as a modal layer with focus trapped inside it, and return focus to the thumbnail that opened it on close.

  2. 2

    Support Escape, a visible close button, a click on the backdrop, and the browser back button. Back must close the viewer rather than leaving the page.

  3. 3

    Show the low-resolution thumbnail immediately and swap in the full image when it loads, so the viewer is never a blank rectangle.

  4. 4

    Support pinch and double-tap zoom on touch, and keyboard zoom and pan on desktop, with a reset to fit.

  5. 5

    Do not load the original file at full resolution on a phone. Request a size appropriate to the viewport and device pixel ratio, or a large photo will exhaust memory and kill the tab.

  6. 6

    The surrounding file list, ordering, and captions are owned by Attachment Gallery; this feature is the viewer only.

Edge cases it handles

6
  • A broken, deleted, or still-processing image must show a clear state inside the viewer, not an empty overlay or a browser error icon.
  • A private image whose signed URL expires while the viewer is open must re-authorize or fail with an explanation.
  • Background scrolling must be locked while open, and restored to the same position on close — including on iOS, where this is not automatic.
  • Swipe to dismiss and swipe to pan conflict once zoomed; dismissal must only apply at the default zoom level.
  • The image needs its alt text carried into the viewer; a decorative thumbnail becoming a focal image without a description is a regression.
  • Very tall or very wide images must fit to the viewport on open rather than opening at native size.

Definition of done

9
  • Focus is trapped while open and restored to the trigger on close.
  • Escape, the close button, the backdrop, and browser back all close the viewer.
  • A placeholder or thumbnail is visible while the full image loads.
  • Zoom works by pinch, double-tap, and keyboard, with a reset to fit.
  • Requested image size is bounded by viewport and device pixel ratio.
  • Broken, private, and processing images each have their own state.
  • Background scroll is locked and restored exactly.
  • The feature matches the existing design system.
  • No existing functionality is broken.

Related features

How it works

  1. 1

    Copy the link

    Grab the Markdown instruction URL for this feature.

  2. 2

    Give it to your AI

    Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.

  3. 3

    It inspects, then implements

    Your agent reads your existing app first, then adds the feature to fit it.

Works with your stack

These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.

Need it tighter than that? Customize the feature and tell it exactly what you're running.