Claude skill · Development · Anthropic
Web app testing skill for Claude
Tests local web apps with Python Playwright: start the servers, inspect the page, then act, with screenshots and browser logs.
- Command
- /webapp-testing
- Licence
- Apache-2.0, copying allowed with attribution
- Folder
- 6 files, 22 KB
- Runs code
- 4 scripts
Overview
What it does
The skill gives Claude a decision tree. For static HTML it reads the file to find selectors. For a dynamic app it starts the servers with scripts/with_server.py if they aren’t already running, waits for the page to settle, takes a screenshot or inspects the DOM, and only then writes the actions.
It tells Claude to run the helper script with --help rather than reading its source, which keeps helper scripts out of the context window: a good example of treating a bundled script as a black box.
Triggers
When Claude uses it
- Checking that a local web app works, debugging UI behaviour, capturing screenshots or reading browser console logs.
Toolkit for interacting with and testing local web applications using Playwright. Supports verifying frontend functionality, debugging UI behavior, capturing browser screenshots, and viewing browser logs.
What it needs
- Python with Playwright and its browsers installed.
Install
How to install it
Claude Code
/plugin marketplace add anthropics/skills
/plugin install example-skills@anthropic-agent-skillsThe example-skills plugin installs 12 skills from this repository, including this one. Its skills are then namespaced, such as /example-skills:webapp-testing.
git clone --depth 1 https://github.com/anthropics/skills.git
mkdir -p ~/.claude/skills
cp -r skills/skills/webapp-testing ~/.claude/skills/That makes it a personal skill, available as /webapp-testing in all your projects. Copy it into .claude/skills/ in a repository instead to share it with your team.
claude.ai and the Claude API
Zip the skill folder, then in claude.ai open Customize > Skills, choose + and Create skill, then Upload a skill. Code execution must be turned on.
from anthropic import Anthropic
from anthropic.lib import files_from_dir
client = Anthropic()
skill = client.skills.create(files=files_from_dir("webapp-testing"))
print(skill.id) # use as a custom skill_id with the code execution toolChecks
SKILL.md validator results
Its SKILL.md (96 lines) run through our SKILL.md validator, with the folder’s file list, for both targets. These check the file’s format, not whether the skill works well.
Claude Code
0 errors, 1 warning, 0 tips
- warningSay when to use it, e.g. “Use when the user asks for…”. Claude matches requests against the description, so it needs both what the skill does and when.
claude.ai and the API
0 errors, 1 warning, 1 tip
- warningSay when to use it, e.g. “Use when the user asks for…”. Claude matches requests against the description, so it needs both what the skill does and when.
- tipThe Claude Help Center’s upload guide gives a 200-character description limit for claude.ai, though the platform docs say 1,024. Keep it under 200 if you’ll upload it there.
Folder
What’s in the folder
- LICENSE.txt11 KB
- SKILL.md3.8 KB
- examples/3 files, 3.4 KB
- scripts/1 file, 3.6 KB
SKILL.md sections
- Web Application Testing
- Decision Tree: Choosing Your Approach
- Example: Using with_server.py
- Reconnaissance-Then-Action Pattern
- Common Pitfall
- Best Practices
- Reference Files
Source
Licence and source
- Published by Anthropic in anthropics/skills/skills/webapp-testing, last changed 2026-04-20.
- Licence: Apache-2.0, copying allowed with attribution. Our copy of the SKILL.md is unmodified, served with its licence.
- Read from commit
dbd4588; write-up checked 2026-10-14. - Before installing, read the SKILL.md on GitHub and its scripts. Anthropic advises using skills only from sources you trust (security considerations).
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