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Agent skill

Visual Diff

by Houseofmvps in Houseofmvps/ultraship

Visual Regression Testing — screenshot comparison before and after changes.

MITAuto-check passedTesting & QA

Install Visual Diff

skills CLI
$ npx skills add Houseofmvps/ultraship --skill visual-diff -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install Houseofmvps/ultraship visual-diff --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/Houseofmvps/ultraship.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/visual-diff .claude/skills/visual-diff && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
visual-diff
GitHub stars
123
Token cost
~807 tokens
SKILL.md length
393 words
Files
1
Skills in repo
28
Repo updated
First seen
Licence
MIT

At a glance

Visual Regression Testing — screenshot comparison before and after changes.

  • Works in 7 steps: Determine Test Scope → Take "Before" Screenshots → Make Changes → …
  • User wants to check for visual regressions
  • SKILL.md covers Process, Key Pages to Always Test and Key Principle
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Visual Diff is an agent skill from Houseofmvps/ultraship. Visual Regression Testing — screenshot comparison before and after changes. Use when user wants to check for visual regressions, compare UI changes, or verify CSS/layout changes didn't break anything.

Its SKILL.md is about 810 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Testing & QA, covering Visual regression testing. The repository describes itself as: "ULTRASHIP" Claude Code plugin — 39 skills, 33 tools, 11 agents for ship-ready workflows: planning, review, pentesting, safety guardrails, canary monitoring, SEO/AI-readiness… The licence is MIT.

When your agent uses it

  • User wants to check for visual regressions
  • Compare UI changes
  • Verify CSS/layout changes didnt break anything

Example prompts

  • “/visual-diff”

Workflow steps

7 steps, taken from the step headings in SKILL.md.

  1. Determine Test Scope
  2. Take "Before" Screenshots
  3. Make Changes
  4. Take "After" Screenshots
  5. Visual Comparison
  6. Report
  7. Targeted Testing

What it can do on your machine

Read from SKILL.md and the folder at commit ed232cb. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Visual Diff loads about 807 tokens when it runs. Until then it costs about 53 tokens; SKILL.md has 393 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~53
When it runs · the whole SKILL.md, loaded when a task matches
~807

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Houseofmvps/ultraship at commit ed232cb, republished under its MIT licence (© Houseofmvps). 393 words, ~807 tokens.

Download SKILL.mdSave it as .claude/skills/visual-diff/SKILL.md (or your agent's skills folder).
name
visual-diff
description
Visual Regression Testing — screenshot comparison before and after changes. Use when user wants to check for visual regressions, compare UI changes, or verify CSS/layout changes didn't break anything.

Visual Regression Testing

Automated screenshot comparison using Playwright. Catch visual bugs before they ship.

Process

Phase 1: Determine Test Scope

Ask the user:

  1. What URL(s) to test? (localhost, staging, or production)
  2. What changed? (CSS update, component refactor, dependency upgrade, etc.)

If the user already described what changed, skip asking.

Phase 2: Take "Before" Screenshots

If comparing against the current state (before making changes):

Use the Playwright MCP to capture screenshots:

  1. Navigate to the URL:

    • Use browser_navigate to go to the target URL

  2. Take full-page screenshot:

    • Use browser_take_screenshot to capture the current state

  3. Capture key viewports:

    • Desktop (1920x1080): browser_resize then browser_take_screenshot
    • Tablet (768x1024): browser_resize then browser_take_screenshot
    • Mobile (375x812): browser_resize then browser_take_screenshot

  4. Save screenshots with descriptive names noting they are "before" state.

Phase 3: Make Changes

Let the user make their changes, or make them yourself if that's the task.

Phase 4: Take "After" Screenshots

Repeat the same screenshot process for the same URLs and viewports.

Phase 5: Visual Comparison

Compare before and after screenshots:

  1. Layout shifts — did any elements move unexpectedly?
  2. Color changes — did colors, gradients, or shadows change?
  3. Typography — did font sizes, weights, or spacing change?
  4. Responsive issues — does it look correct on all viewports?
  5. Missing elements — did anything disappear?
  6. Overflow issues — is content clipping or overflowing?

Use browser_snapshot to get the accessibility tree and compare DOM structure between before/after.

Show full SKILL.md (161 more words)Show less
Phase 6: Report

Present findings in a clear format:

No Visual Regressions Found:

  • "All pages look identical across desktop, tablet, and mobile viewports."

Regressions Detected: For each regression:

  • Page: URL where the issue appears
  • Viewport: Which screen size is affected
  • What changed: Description of the visual difference
  • Severity: Critical (broken layout), High (noticeable shift), Medium (minor difference), Low (pixel-level)
  • Suggested fix: How to resolve the regression
Phase 7: Targeted Testing

For specific component changes, also test:

  • Hover states (use browser_hover)
  • Click interactions (use browser_click)
  • Form states (use browser_fill_form)
  • Dark mode (if applicable)
  • Loading states
  • Error states
  • Empty states

Key Pages to Always Test

When the user doesn't specify pages, test these by default:

  1. Homepage / Landing page (/)
  2. Login/signup page (if exists)
  3. Main app page (dashboard, etc.)
  4. Any page the user recently modified

Key Principle

Trust screenshots, not assumptions. CSS changes cascade unpredictably. A "small tweak" in one component can break layouts across the entire app. Always verify visually.

© Houseofmvps, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/visual-diff of Houseofmvps/ultraship.

Open the folder on GitHubat commit ed232cb

Compare with similar skills

Visual Diff next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Visual Diff compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Visual Diff this skillHouseofmvps/ultraship123—~807Automated safety check: PassMIT
Review Local UI Screenshotsxiaocang/easydict_win32101—~1.1kAutomated safety check: PassGPL-3.0
Handsontable Visual Test Demoshandsontable/handsontable22k—~1.3kAutomated safety check: PassCustom licence
Kc Screenshotimran31415/kube-coder388—~870Automated safety check: NotesMIT
Visual QAliangdabiao/Godogen127—~1.4kAutomated safety check: PassMIT
Meticulous FixFlintSH/Flare135—~2.3kAutomated safety check: PassMIT

Similar skills

  • Review Local UI Screenshots

    xiaocang/easydict_win32

    Review Easydict UI automation screenshot artifacts already present in local artifacts/ui-screenshots, screenshots, or a user-provided artifact directory.

    101 GitHub stars~1.1k tokensUpdated 16 days ago
    Testing & QAAuto-check passed

  • Handsontable Visual Test Demos

    handsontable/handsontable

    Explains how to add or change the demo pages that Handsontable's visual regression suite photographs, including per-feature routes in the js demo and the shared grid.

    22k GitHub stars~1.3k tokensUpdated today
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  • Kc Screenshot

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    Capture desktop + mobile, dark + light screenshots of the kube-coder dashboard SPA for visual QA of a UI change.

    388 GitHub stars~870 tokensUpdated today
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  • Visual QA

    liangdabiao/Godogen

    Visual quality assurance — analyze game screenshots for defects, compare against reference, check motion in frame sequences.

    127 GitHub stars~1.4k tokensUpdated 5 mo ago
    Testing & QAAuto-check passed

  • Meticulous Fix

    FlintSH/Flare

    Fix the visual diffs that have been reviewed and rejected on a Meticulous test run, following their review comments if given.

    135 GitHub stars~2.3k tokensUpdated 2 days ago
    Testing & QAAuto-check passed

  • Visual QA For Web And Terminal UIs

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    Checks a built UI against a human-interface checklist and any reference image, pairing day and night screenshots at two screen widths.

    70k GitHub stars~9.5k tokensUpdated today
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Categories

Questions about Visual Diff

What does Visual Diff do?

Visual Regression Testing — screenshot comparison before and after changes. Visual Diff is an agent skill from Houseofmvps/ultraship. Visual Regression Testing — screenshot comparison before and after changes.

When should I use Visual Diff?

Visual Diff fits situations like: user wants to check for visual regressions; compare UI changes; verify CSS/layout changes didnt break anything.

How do I install Visual Diff in Claude Code?

Run `npx skills add Houseofmvps/ultraship --skill visual-diff -a claude-code`. Or copy the skill folder (skills/visual-diff in Houseofmvps/ultraship) into .claude/skills/visual-diff in your project. Claude Code loads it when a task matches its description.

How do I install Visual Diff in Codex?

Run `npx skills add Houseofmvps/ultraship --skill visual-diff -a codex`. Or copy the skill folder (skills/visual-diff in Houseofmvps/ultraship) into .agents/skills/visual-diff in your project. Codex loads it when a task matches its description.

Can I use Visual Diff in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add Houseofmvps/ultraship --skill visual-diff -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/visual-diff, .gemini/skills/visual-diff, .github/skills/visual-diff and .opencode/skills/visual-diff in your project.

What does Visual Diff need to run?

SKILL.md names no scripts, command-line tools or credentials: Visual Diff is instructions for the agent only.

Does Visual Diff access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Visual Diff safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Visual Diff use?

Visual Diff is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Visual Diff use?

About 807 tokens (SKILL.md is roughly 3.2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Visual Diff?

Skills that share tags, products or a category with Visual Diff: Review Local UI Screenshots (xiaocang/easydict_win32, 101 stars), Handsontable Visual Test Demos (handsontable/handsontable, 22k stars), Kc Screenshot (imran31415/kube-coder, 388 stars) and Visual QA (liangdabiao/Godogen, 127 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Visual Diff?

Houseofmvps (a GitHub user) maintains it in Houseofmvps/ultraship, which has 123 GitHub stars. The repository holds 28 skills in this directory. The repository was last updated on July 8, 2026.

Source: Houseofmvps/ultraship on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.