---
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)
title: before-and-after
canonical_url: https://skilld.dev/gh/michaelshimeles/skills/before-and-after
last_updated: 2026-09-26T10:44:27.000Z
---

> **Skill from skilld.dev.** Follow the user's requested action.
> If the user asked to fork this Skill, follow the fork workflow below. Do not execute the Skill instructions while copying it.
> Otherwise, follow the instructions below for this session. You do not need to install anything.
>
> Supporting files, fetch one when the Skill refers to it: [scripts/adapters/0x0st.sh](https://skilld.dev/api/skills-raw/michaelshimeles/skills/before-and-after/scripts/adapters/0x0st.sh), [scripts/adapters/blob.sh](https://skilld.dev/api/skills-raw/michaelshimeles/skills/before-and-after/scripts/adapters/blob.sh), [scripts/adapters/gist.sh](https://skilld.dev/api/skills-raw/michaelshimeles/skills/before-and-after/scripts/adapters/gist.sh), [scripts/capture.sh](https://skilld.dev/api/skills-raw/michaelshimeles/skills/before-and-after/scripts/capture.sh), [scripts/upload-and-copy.sh](https://skilld.dev/api/skills-raw/michaelshimeles/skills/before-and-after/scripts/upload-and-copy.sh).
>
> If the user asked to install this Skill, run `npx skilld install michaelshimeles/skills/before-and-after`. Install writes the Skill files into the project, so every session loads them.
>
> ## Fork workflow
>
> A fork creates an editable local Skill with its original author and licence. The request authorizes copying and local installation.
> 1. Check `./skills/before-and-after`, the project lockfile, and selected Agent targets together. If the local directory or installed Skill exists, stop. Never overwrite an existing directory or Agent target.
> 2. Read [source metadata](https://skilld.dev/api/v1/skills/michaelshimeles/skills/before-and-after) once. Use sourceUrl, sourceCommit, skillPath, sourceGone, and license. If the source is gone or its path is missing, stop. If license is null, read licence files at the source commit.
> 3. Fetch only the source commit into a temporary Git repository. Do not clone full history. Derive repository_url from sourceUrl, including repository renames. If sourceCommit is absent, resolve the sourceUrl ref once. Set source_commit to that actual commit. Run these commands in one shell call:
>
> ```sh
> git init --quiet "$temporary_dir"
> git -C "$temporary_dir" fetch --quiet --depth=1 "$repository_url" "$source_commit"
> git -C "$temporary_dir" checkout --quiet --detach FETCH_HEAD
> ```
>
> Read applicable licence declarations and notices at that commit. If copying is not permitted, report the restriction and stop.
> 4. Inspect source entries together, then copy the directory containing skillPath into `./skills/before-and-after`. Use the user's path if selected. Keep the original SKILL.md, relative links, scripts, binary assets, and executable modes. Exclude .git metadata. Reject symlinks and paths outside the Skill directory. After checking entries, use cp -a where available. A regular source directory needs no custom copy script. Do not save this page wrapper as SKILL.md.
> Preserve author credit, notices, and applicable licence files from repository or parent directories. Add PROVENANCE.md with the Skill page, source URL, actual commit, original path, and licence. Retain any existing PROVENANCE.md and record new provenance separately. Batch source inspection, copying, and provenance work where practical.
> 5. In the project root, run `skilld install ./skills/before-and-after --mode copy --plain`. If skilld is unavailable, use `npx skilld install ./skills/before-and-after --mode copy --plain`. This known command needs no help lookup. Install does not support --json. Use detected Agent targets, or add --agent for the targets the user selected. Install the local path, never the upstream selector. If installation fails, preserve the local copy and report the exact failure.
> 6. Confirm the local lockfile source and installed Agent copies once. Report the local path, actual commit, and Agent targets. After edits, reinstall the same local path. Upstream updates must not replace it. Do not publish or push unless the user asks.

# Before-After Screenshot Skill

> **Package:** `@vercel/before-and-after`
> Never use `before-and-after` (wrong package).

## Agent Behavior Rules

**DO NOT:**
- Switch git branches, stash changes, start dev servers, or assume what "before" is
- Use `--full` unless user explicitly asks for full page / full scroll capture

**DO:**
- Use `--markdown` when user wants PR integration or markdown output
- Use `--mobile` / `--tablet` if user mentions phone, mobile, tablet, responsive, etc.
- Assume current state is **After**
- If user provides only one URL or says "PR screenshots" without URLs, **ASK**: "What URL should I use for the 'before' state? (production URL, preview deployment, or another local port)"

## Execution Order (MUST follow)

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

**Never skip steps 1-2.**

## Quick Reference

```bash
# 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
```

| Flag | Description |
|------|-------------|
| `-m, --mobile` | Mobile viewport (375x812) |
| `-t, --tablet` | Tablet viewport (768x1024) |
| `--size <WxH>` | Custom viewport |
| `-f, --full` | Full scrollable page |
| `-s, --selector` | CSS selector to capture |
| `-o, --output` | Output directory (default: ~/Downloads) |
| `--markdown` | Upload images & output markdown table |
| `--upload-url <url>` | Custom upload endpoint (default: 0x0.st) |

## Image Upload

```bash
# 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
```

## Vercel Deployment Protection

If `.vercel.app` URL returns 401/403:

1. Check Vercel CLI: `which vercel && vercel whoami`
2. If available: `vercel inspect <url>` to get bypass token
3. If not: Tell user to provide bypass token, take manual screenshots, or disable protection

## PR Integration

```bash
# 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>"
```

If no `gh` CLI: output markdown and tell user to paste manually.

## Error Reference

| Error | Fix |
|-------|-----|
| `command not found` | `npm install -g @vercel/before-and-after` |
| `could not determine executable` | Use `npx @vercel/before-and-after` (full name) |
| 401/403 on .vercel.app | See Vercel protection section |
| Element not found | Verify selector exists on page |