Locale and Language Switcher
Let people change language without losing their place or seeing half a translation.
What it adds
A locale selector wired into routing and persistence, with sane fallbacks when a translation is missing.
What your agent is told to do
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What your agent is told to do
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Decide how locale is carried before building the switcher: a URL path segment, a subdomain, or a stored preference. The URL is the only one that survives sharing and indexing.
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Resolve the active locale in a fixed order — explicit URL, saved user preference, Accept-Language header, then default — and apply the same order on the server and the client.
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Switching must land the user on the equivalent page in the new locale, not on the home page.
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Fall back per key to the default locale when a translation is missing, and log the miss so it can be filled. Never render a raw key like users.profile.title to a person.
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Set the document language and direction attributes from the active locale, and support right-to-left layout where a supported locale requires it.
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Do NOT infer the language from IP geolocation. Country is not language, and overriding an explicit choice with a guess is worse than showing the default.
Edge cases it handles
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Edge cases it handles
7- The server-rendered locale must match what the client resolves, or hydration mismatches will flash the wrong language.
- A saved preference must not silently override an explicit locale in the URL — the URL wins, and it should update the saved preference.
- An entire missing locale should degrade to the default cleanly rather than producing a page of empty strings.
- Pluralization rules differ by language; a two-form English rule breaks in locales with more forms.
- User-generated content is not translated. Do not run it through the translation layer or label it with the interface locale.
- Right-to-left flips layout, icons with direction, and scroll position — mirroring the text alone leaves a broken page.
- Emails, PDFs, and other out-of-band output need the recipient's stored locale, not the locale of whoever triggered them.
Definition of done
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Definition of done
9- Locale resolution follows one documented order on both server and client.
- Switching language keeps the user on the equivalent route.
- The choice persists across sessions but never overrides an explicit URL locale.
- Missing keys fall back to the default locale and are logged; no raw keys are ever rendered.
- There is no hydration mismatch or flash of the wrong language.
- Document language and direction attributes reflect the active locale, and RTL layouts are correct.
- Emails and generated documents use the recipient's locale.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Focus Ring System
Focus Ring System
Give every focusable control one clear focus indicator that belongs to the design.
What it does
A single focus treatment applied consistently across buttons, links, inputs, cards, rows, and custom controls.
How it works
- 1 Inventory every focusable element in the app, including the ones made focusable by hand — clickable rows, cards, canvas objects, custom selects — and confirm each shows the shared treatment.
- 2 Distinguish focus arriving from the keyboard from focus arriving from a click, and show the ring for keyboard and programmatic focus. A ring appearing on every mouse press reads as a rendering fault and invites someone to remove it entirely.
- 3 Compose the ring so it stays visible on every surface the control can sit on: page background, card, coloured button, dark toolbar, selected row. A single-colour ring will disappear against at least one of them.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/focus-ring-system
Auto Captions
Auto Captions
Every uploaded video gets timed captions without anyone typing them out.
What it does
An automatic captioning pass over uploaded video that produces a timed caption track shown in the player.
How it works
- 1 Extend the app's existing Voice Transcription rather than adding a second speech pipeline. What is new here is timing, storage as a caption track, and player integration, not the recognition itself.
- 2 Run captioning as a background job triggered after the upload finishes, and reuse the app's existing job progress reporting so the user can see where a long file has got to.
- 3 Store the caption track as its own record linked to the media, with a language, a status, and a source marking it as machine-generated so a human correction can supersede it later.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/auto-captions
Touch Target Checker
Touch Target Checker
Find the controls that are too small or too crowded to hit reliably on a phone.
What it does
A development-time audit reporting the measured hit area and neighbour spacing of every interactive element.
How it works
- 1 Measure the element's actual activation area — the region that responds to a tap — rather than the icon or glyph drawn inside it, since padding and pseudo-element extensions frequently make a small icon a perfectly adequate target.
- 2 Check the gap between adjacent targets as well as their size. Two comfortable buttons sitting flush against each other still produce mis-taps, and the report must say which of the two problems it found.
- 3 Report the offending elements with enough context to locate them — the route, the component, and a way to highlight the element on the page — rather than a count of failures.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/touch-target-checker
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.