Viewport Height Utility
Stop full-height screens from jumping or hiding their controls on mobile browsers.
What it adds
A single shared height primitive that resolves to the real usable viewport on every device and browser mode.
What your agent is told to do
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What your agent is told to do
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Find every place the app assumes the viewport is a fixed height — full-bleed heroes, sidebars, drawers, editor shells, scroll containers with a hard height — and route them all through one shared height primitive rather than repeating the same measurement in a dozen components.
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Distinguish the three heights that matter and pick deliberately per surface: the smallest height the viewport takes when browser chrome is fully expanded, the largest when it is retracted, and the height right now. A fixed sidebar wants the small height so its footer is never cut off; a decorative hero can take the large height.
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Always pair the viewport height with a content minimum. A panel that collapses to the height of a short phone in landscape must still be tall enough to show its own controls, and must scroll rather than crush its contents.
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Verify the behaviour in a normal browser tab, in a home-screen installed session with no browser chrome at all, and in landscape, because each resolves the same declaration to a different number and only one of them is usually tested.
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Do not measure the window in script and write a pixel height on resize. That approach fires late, flashes the wrong height on first paint, fights browser chrome that animates in and out during a scroll, and has to be re-run for every orientation and keyboard event.
Edge cases it handles
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Edge cases it handles
7- Mobile browsers change their visible height as the address bar retracts and expands during a scroll, so a naive full-height value is correct at rest and wrong mid-scroll. Choose the small or large viewport variant explicitly per surface rather than accepting whichever the browser reports at the moment of layout.
- When the on-screen keyboard opens, the usable area shrinks dramatically and any element sized to the full viewport will push its own footer and primary action underneath the keyboard. Decide per surface whether it tracks the shrunken viewport or holds still, and never let a submit control end up unreachable.
- A viewport height must never become a content ceiling. If the content is taller than the resolved height — a long form, a translated label that wraps to three lines, a large accessibility text size — the container must scroll instead of clipping, so enforce a minimum height alongside the viewport height.
- The same declaration resolves differently in a browser tab, in a home-screen standalone session, and inside an in-app webview, because each has a different amount of surrounding chrome. All three need checking, and standalone mode also has to clear the device safe-area insets at the top and bottom.
- Rotating the device changes both the height and the amount of chrome at once, and some browsers report the old value for a frame or two afterwards. The layout must settle correctly without the user needing to scroll to trigger a reflow.
- Nested full-height containers compound the error: a panel that is one full viewport tall inside another that is also one full viewport tall produces a page twice the screen height with no visible scroll cue.
- Height changes must not be animated by default. A container that eases between the small and large viewport height turns ordinary scrolling into a wobbling layout.
Definition of done
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Definition of done
8- Every full-height surface in the app resolves its height through one shared primitive rather than a locally repeated calculation.
- Scrolling on a mobile browser does not resize, jump, or reflow full-height layouts as the address bar retracts.
- No primary action or footer control is pushed out of reach when the on-screen keyboard is open.
- Full-height containers scroll rather than clip when their content exceeds the resolved height.
- The layout is correct in a browser tab, in a home-screen standalone session, and after rotating the device.
- Safe-area insets are respected at the top and bottom in standalone mode.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Beautiful Empty States
Beautiful Empty States
Replace blank screens with useful, contextual empty states.
What it does
Every list, table, and dashboard in your app has a "nothing here yet" state. Most
apps ship a blank rectangle — and it is often the very first thing a new user sees.
An empty state should say what belongs here, why it is empty, and what to do next.
How it works
- 1 Inventory the empty cases first. List every collection view in the app and
- 2 Distinguish the three kinds of empty. They are not the same, and must not
- 3 Build one reusable empty-state component from the existing design system,
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/beautiful-empty-states
Opening Hours Display
Opening Hours Display
Say whether you are open right now and when you next open.
What it does
A live open or closed state alongside the weekly hours, with holiday closures folded in.
How it works
- 1 Lead with the current state in plain words and follow it with the next transition: open until a time, or closed until a day and time. The weekly table is supporting detail, not the headline.
- 2 Store hours as intervals against the business's own zone, and keep holiday and one-off closures as overrides that win over the regular week rather than as edits to it.
- 3 Compute the state on the server for the first render so the page does not briefly claim the wrong thing, then let the page update itself as the clock crosses a boundary without a reload.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/opening-hours-display
Dark Mode
Dark Mode
Add a dark theme that respects the system preference and the user's choice.
What it does
A complete dark theme, defaulting to the operating system preference and overridable by the user.
How it works
- 1 Audit every colour in the app first and report where they are defined. If colours are hardcoded throughout, extract them into tokens before anything else — that refactor is the bulk of this work.
- 2 Define a dark palette against those tokens. Do not simply invert the light theme.
- 3 Default to the system preference via prefers-color-scheme, and let the user override it.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/dark-mode
How it works
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1
Copy the link
Grab the Markdown instruction URL for this feature.
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Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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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.