Before and After Screenshots

What it does

When your agent uses it

• Documenting a UI change with before and after screenshots for a PR
• Comparing a production page with a preview deployment visually
• Capturing mobile or tablet views of two versions of a page

Example prompts

• “Take before and after screenshots of the pricing page, production versus the preview URL, and format them for a PR.”
• “Compare these two screenshots, old.png and new.png, side by side.”
• “Capture the header element only on mobile for both versions.”

Requirements

• Node.js with npm, to install `@vercel/before-and-after`
• GitHub CLI `gh`, only for editing a PR
• Vercel CLI, only for protected preview URLs
• Pre-approved tools (allowed-tools): Bash(npx @vercel/before-and-after *), Bash(before-and-after *), Bash(which before-and-after), Bash(npm install -g @vercel/before-and-after), Bash(*/upload-and-copy.sh *), Bash(curl -s -o /dev/null -w *), Bash(gh pr view *), Bash(gh pr edit *), Bash(vercel inspect *), Bash(vercel whoami), Bash(which vercel), Bash(which gh)

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

1. 1Pre-flight — which before-and-after || npm install -g @vercel/before-and-after
2. 2Protection check — if .vercel.app URL: curl -s -o /dev/null -w "%{http_code}" "" (401/403 = protected)
3. 3Capture — before-and-after "" ""
4. 4Upload — ./scripts/upload-and-copy.sh --markdown
5. 5PR integration — optionally gh pr edit to append markdown

What it can do on your machine

Read from SKILL.md and the folder at commit 4b72f46. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Bash(npx @vercel/before-and-after *)
  • Bash(before-and-after *)
  • Bash(which before-and-after)
  • Bash(npm install -g @vercel/before-and-after)
  • Bash(*/upload-and-copy.sh *)
  • Bash(curl -s -o /dev/null -w *)
  • Bash(gh pr view *)
  • Bash(gh pr edit *)
  • Bash(vercel inspect *)
  • Bash(vercel whoami)

  …and 2 more on the same allowed-tools line.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 5 files in scripts/ (Shell), which the agent can run.

  Shell commands in SKILL.md call:

  • gh
  • npx
  • npm
  • vercel
  • curl

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

• Network

  No URLs in SKILL.md. Its commands use gh, npx, npm, vercel and curl, which can reach the network depending on how they are called.

  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

Before and After Screenshots loads about 1k tokens when it runs. Until then it costs about 81 tokens; SKILL.md has 289 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~81

When it runs · the whole SKILL.md, loaded when a task matches

~1k

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

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); the scripts in this folder are not scanned.

SKILL.md

The full file from michaelshimeles/skills at commit 4b72f46, republished under its MIT licence (© michaelshimeles). 289 words, ~1,010 tokens.

name

before-and-after

description

Captures before/after screenshots of web pages or elements for visual comparison. Use when user says "take before and after", "screenshot comparison", "visual diff", "PR screenshots", "compare old and new", or needs to document UI changes. Accepts two URLs (file://, http://, https://) or two image paths.

allowed-tools

Bash(npx @vercel/before-and-after *), Bash(before-and-after *), Bash(which before-and-after), Bash(npm install -g @vercel/before-and-after), Bash(*/upload-and-copy.sh *), Bash(curl -s -o /dev/null -w *), Bash(gh pr view *), Bash(gh pr edit *), Bash(vercel inspect *), Bash(vercel whoami), Bash(which vercel), Bash(which gh)

# Basic usage
before-and-after <before-url> <after-url>

# With selector
before-and-after url1 url2 ".hero-section"

# Different selectors for each
before-and-after url1 url2 ".old-card" ".new-card"

# Viewports
before-and-after url1 url2 --mobile    # 375x812
before-and-after url1 url2 --tablet    # 768x1024
before-and-after url1 url2 --full      # full scroll

# From existing images
before-and-after before.png after.png --markdown

# Via npx (use full package name!)
npx @vercel/before-and-after url1 url2

# Default (0x0.st - no signup needed)
./scripts/upload-and-copy.sh before.png after.png --markdown

# GitHub Gist
IMAGE_ADAPTER=gist ./scripts/upload-and-copy.sh before.png after.png --markdown

# Check for gh CLI
which gh

# Get current PR
gh pr view --json number,body

# Append screenshots to PR body
gh pr edit <number> --body "<existing-body>

## Before and After
<generated-markdown>"

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

Files

SKILL.md and 6 other files (scripts) in before-and-after of michaelshimeles/skills.

• SKILL.md
• LICENSE
• scripts/adapters/0x0st.sh
• scripts/adapters/blob.sh
• scripts/adapters/gist.sh
• scripts/capture.sh
• scripts/upload-and-copy.sh

Open the folder on GitHubat commit 4b72f46

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in michaelshimeles/skills, which our catalogue first saw on October 7, 2026.

• boringcomputers/goshen-email.claude/skills/before-and-after