In-App Contrast Checker
Measure contrast against what actually rendered, not against what the stylesheet claimed.
What it adds
A development-mode checker that samples real rendered foreground and background pairs and reports the ones that fail.
What your agent is told to do
5
What your agent is told to do
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Read the computed style of each element and the effective colour behind it, walking up through ancestors until an opaque background is found. Source values in the stylesheet are not what the user sees once inheritance, overrides, and alpha have been applied.
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Evaluate text and non-text separately against their own thresholds — body copy, large headings, icons, focus rings, and control borders do not share one number, and applying a single threshold produces both false failures and false passes.
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Handle the cases where there is no single background colour: partial opacity, gradients, photographic images, and video. Sample the actual composited pixels behind the text and report the worst region rather than the average.
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Report the failure with the offending element, its two colours, the measured ratio, and the nearest token that would pass. Do not mutate the theme to fix it — correcting the ramp belongs to Brand Palette Generator, and correcting the mapping belongs to Semantic Color Tokens.
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Keep the checker out of the production bundle and out of the normal render path. A contrast pass that runs on every paint in front of customers is a performance regression sold as an accessibility feature.
Edge cases it handles
7
Edge cases it handles
7- Text sitting on a gradient, a photograph, or a partially transparent panel has no single background colour — sample the composited result across the text's own bounds and report the weakest point, not a convenient average.
- Text and non-text elements are held to different thresholds, and large text to a different threshold again, so the checker must classify each element by rendered size and weight before judging it.
- Computed styles are the only honest source. A component whose colour comes from an inherited variable, a utility class, or an inline override will report a passing source value and a failing rendered one.
- The checker suggests; it never edits. Silently rewriting a theme to satisfy a ratio produces a palette nobody chose and hides the original decision that caused the failure.
- Elements that are hidden, clipped to zero size, or positioned off-screen must be skipped, or the report fills with failures nobody can see or act on.
- Disabled controls and purely decorative text are exempt by specification — flagging them trains people to ignore the whole report.
- Running the check while a transition is mid-flight samples an intermediate colour; wait for the element to settle before measuring.
Definition of done
9
Definition of done
9- The checker reads computed and composited values, not stylesheet source values.
- Text and non-text elements are judged against separate, correct thresholds.
- Text over gradients, images, and translucent surfaces is measured against the pixels actually behind it.
- Each failure names the element, both colours, the measured ratio, and a passing alternative.
- No theme value is changed by the checker itself.
- Hidden, off-screen, disabled, and decorative elements are excluded from the report.
- The checker is absent from production builds.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
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
Accessible Name Validator
Accessible Name Validator
Find every control a screen reader announces as nothing useful.
What it does
An audit of the computed accessible name of each interactive element in the rendered interface.
How it works
- 1 Compute the name the way assistive technology does — following the resolution order through labels, referenced elements, attributes, and text content — rather than reading the source markup and guessing.
- 2 Report three separate failures: an empty name, a generic name such as button, link, or here, and duplicate names within the same context where several controls announce identically.
- 3 Prefer a fix that adds a visible label. A control given a hidden name is announced but still mysterious to the sighted user who cannot tell two identical icons apart.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/accessible-name-validator
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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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.