Guide · Agent skill
How to use the Dark Mode CSS Checker agent skill
Updated · written with AI from the project's own documentation and checked against our catalogue data
The dark-mode-css skill is a review guide for AI coding agents. Once it is installed, the agent reads your stylesheets and component styles, checks whether they handle dark mode through prefers-color-scheme or a data-theme attribute, and points out hard-coded colors that would look wrong in a dark theme. This guide explains what the skill does, how to install it, how to trigger it, and what to expect from it.
Dark Mode CSS Checkerthedaviddias/Front-End-Checklist · MIT Download the skill Quick start
- 1Download the ZIP. Download the dark-mode-css skill ZIP from this page.
- 2Unzip the skill folder. Unzip it into ~/.claude/skills/ for personal use, or into a project's .claude/skills/ folder.
- 3Or upload it in the Claude apps. Go to Settings, then Capabilities, then Skills, and upload the skill.
- 4Ask for a review in plain language. Mention your stylesheet or component and dark mode support.
- 5Check the findings. Look at the flagged selectors, hard-coded colors and suggested custom properties.
- 6Verify in a browser. Test contrast, breakpoints and interaction states yourself before applying changes.
What does the dark-mode-css skill make the agent do?
The skill is based on the Front-End Checklist rule 'Support dark mode with prefers-color-scheme'. It changes how the agent reads and advises on CSS. It does not add a tool, a build step or a visual tester.
When you ask for a review, the agent looks for prefers-color-scheme usage or a data-theme attribute pattern, and identifies hard-coded colors that would look wrong in dark mode. It then suggests moving colors into CSS custom properties redefined inside a prefers-color-scheme: dark media query, and checks contrast and layouts before proposing fixes.
- Checks whether the CSS supports dark mode via prefers-color-scheme or a data-theme attribute
- Flags hard-coded colors that would look wrong in dark mode
- Suggests extracting colors to CSS custom properties on :root
- Keeps contrast ratios (WCAG) in mind when proposing dark colors
Install the dark-mode-css skill
Download the ZIP file for the skill from this page and unzip it. The skill folder contains SKILL.md and references/rule.md.
For a personal install, unzip the skill into ~/.claude/skills/. For a single project, put it in the project's .claude/skills/ folder instead.
You can also upload the skill in the Claude apps. Go to Settings, then Capabilities, then Skills, and upload it there.
- Personal: ~/.claude/skills/
- Project only: .claude/skills/ inside the project
- Claude apps: Settings → Capabilities → Skills
How do you trigger the skill with a natural request?
You do not need a special command. Ask for what you need in plain language and mention stylesheets or dark mode. The skill's description covers reviewing stylesheets, component styles and responsive behavior related to supporting dark mode with prefers-color-scheme.
Naming the file or component makes the review more precise, because the skill asks the agent to flag exact selectors, declarations or breakpoints that violate the rule.
- "Review styles/app.css for dark mode support."
- "Does this button component handle prefers-color-scheme? Flag any hard-coded colors."
- "Suggest how to move these colors into CSS custom properties with a dark media query."
What does the skill need and what are its safety notes?
The skill lists no requirements. It does not run scripts and does not use the network, so it only reads the files you give it and the agent's answers are based on that reading.
Because the files include no tool that renders pages, the agent reasons about layouts rather than seeing them. Do not expect automatic or verified visual testing. Check the proposed changes in a real browser yourself.
- Requires: nothing listed
- Runs scripts: no
- Uses network: no
- No rendering tool is included, so layout checks are reasoning, not screenshots
What does a good dark mode fix look like?
The reference rule recommends defining semantic color tokens such as --color-surface and --color-text on :root, then redefining the same variables inside @media (prefers-color-scheme: dark). Component styles stay unchanged because they reference the tokens.
The rule also mentions a manual toggle: store the preference in localStorage and set a data-theme attribute. Ask the agent to cover this if your site needs a user-facing switch.
- Use semantic names, not color names
- Redefine the same variables in the dark media query
- Keep component rules pointing at the variables
:root { --color-surface: #ffffff; --color-text: #111827; }
@media (prefers-color-scheme: dark) { :root { --color-surface: #0f172a; } }Tips for getting useful results
Give the agent the stylesheets or component files directly, and say which pages or components matter most. The more specific the request, the more specific the findings.
Treat the output as a checklist to verify, not a final answer. Confirm contrast with your own tools and check breakpoints and interaction states in the browser.
- Start with one component or one stylesheet
- Ask for exact selectors and declarations in the output
- Verify contrast and layouts yourself before shipping
What people use it for
- Reviewing a legacy stylesheet to see which colors would break in dark mode
- Checking whether a component library's styles use prefers-color-scheme or a data-theme attribute
- Planning a move from hard-coded hex values to CSS custom properties
- Running a Front-End Checklist style review of responsive and dark theme behavior
Frequently asked questions
Is the dark-mode-css skill free?
The skill is published under the MIT licence, as listed on this page. Check the licence file in the source repository for the full terms.
What do I need to install the dark-mode-css skill?
The skill lists no requirements. You download the ZIP from this page and unzip it into ~/.claude/skills/ or a project's .claude/skills/ folder, or upload it in the Claude apps under Settings, Capabilities, Skills.
Does the skill run scripts or use the internet?
No. The skill runs no scripts and uses no network. It works by changing how the agent reads and advises on your CSS.
Does the skill test my site visually?
No. The files include no tool that renders pages, so the agent reasons about layouts rather than testing them. Check results in a real browser.
How is this different from a dark mode CSS generator or a visual testing tool?
This skill is a review guide based on a checklist rule. A visual testing tool renders pages and compares them, which this skill does not do.
Why use prefers-color-scheme instead of a toggle?
Using prefers-color-scheme respects the user's OS preference without a toggle. The rule also covers adding a manual toggle with localStorage and a data-theme attribute if you need one.
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Our verdict
Front-end developers adding dark mode to an existing stylesheet, and reviewers checking whether CSS handles dark themes, will get a useful checklist-based review. If you need automatic visual testing, or your project has no stylesheets, pick a tool that renders pages or skip this skill.
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