Web Artifacts Builder
anthropics/skills
Builds multi-component claude.ai HTML artifacts as a small React, TypeScript and Tailwind project, then bundles it into one shareable HTML file.
“Send-ready single-file email”
Install HTML Email
$ npx skills add asgeirtj/system_prompts_leaks --skill html-email -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install asgeirtj/system_prompts_leaks html-email --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/asgeirtj/system_prompts_leaks.git skills-src && mkdir -p .claude/skills && cp -r skills-src/Anthropic/claude-design/skills/html-email .claude/skills/html-email && rm -rf skills-srcUse ~/.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/
Install the "html-email" agent skill from https://github.com/asgeirtj/system_prompts_leaks/tree/main/Anthropic/claude-design/skills/html-email into .claude/skills/html-email/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "html-email", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/asgeirtj/system_prompts_leaks/tree/main/Anthropic/claude-design/skills/html-emailType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add asgeirtj/system_prompts_leaks --skill html-email -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install asgeirtj/system_prompts_leaks html-email --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/asgeirtj/system_prompts_leaks.git skills-src && mkdir -p .agents/skills && cp -r skills-src/Anthropic/claude-design/skills/html-email .agents/skills/html-email && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "html-email" agent skill from https://github.com/asgeirtj/system_prompts_leaks/tree/main/Anthropic/claude-design/skills/html-email into .agents/skills/html-email/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "html-email", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add asgeirtj/system_prompts_leaks --skill html-email -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install asgeirtj/system_prompts_leaks html-email --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/asgeirtj/system_prompts_leaks.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/Anthropic/claude-design/skills/html-email .cursor/skills/html-email && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "html-email" agent skill from https://github.com/asgeirtj/system_prompts_leaks/tree/main/Anthropic/claude-design/skills/html-email into .cursor/skills/html-email/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "html-email", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/asgeirtj/system_prompts_leaks.git --path Anthropic/claude-design/skills/html-email--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add asgeirtj/system_prompts_leaks --skill html-email -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install asgeirtj/system_prompts_leaks html-email --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/asgeirtj/system_prompts_leaks.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/Anthropic/claude-design/skills/html-email .gemini/skills/html-email && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "html-email" agent skill from https://github.com/asgeirtj/system_prompts_leaks/tree/main/Anthropic/claude-design/skills/html-email into .gemini/skills/html-email/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "html-email", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install asgeirtj/system_prompts_leaks html-emailInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add asgeirtj/system_prompts_leaks --skill html-email -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/asgeirtj/system_prompts_leaks.git skills-src && mkdir -p .github/skills && cp -r skills-src/Anthropic/claude-design/skills/html-email .github/skills/html-email && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "html-email" agent skill from https://github.com/asgeirtj/system_prompts_leaks/tree/main/Anthropic/claude-design/skills/html-email into .github/skills/html-email/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "html-email", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add asgeirtj/system_prompts_leaks --skill html-email -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install asgeirtj/system_prompts_leaks html-email --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/asgeirtj/system_prompts_leaks.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/Anthropic/claude-design/skills/html-email .opencode/skills/html-email && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "html-email" agent skill from https://github.com/asgeirtj/system_prompts_leaks/tree/main/Anthropic/claude-design/skills/html-email into .opencode/skills/html-email/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "html-email", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
html-email- GitHub stars
- 69k
- Token cost
- ~659 tokens
- SKILL.md length
- 360 words
- Files
- 1
- Skills in repo
- 128
- Repo updated
- First seen
- Licence
- CC0-1.0
At a glance
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
About this skill
HTML Email is a skill in asgeirtj/system_prompts_leaks (69k stars). Its SKILL.md is about 659 tokens. Licence: CC0-1.0.
What it can do on your machine
Read from SKILL.md and the folder at commit 60d44cc. 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
HTML Email loads about 659 tokens when it runs. Until then it costs about 10 tokens; SKILL.md has 360 words of instructions outside code blocks.
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 asgeirtj/system_prompts_leaks at commit 60d44cc, republished under its CC0-1.0 licence (© asgeirtj). 360 words, ~659 tokens.
Download SKILL.mdSave it as
.claude/skills/html-email/SKILL.md (or your agent's skills folder).- name
- html-email
- description
- Send-ready single-file email
- user-invocable
- true
HTML email
Design an HTML email as ONE self-contained .html file that survives real email clients. Email rendering is not browser rendering — Gmail, Outlook, and Apple Mail each strip or mangle different things, and the rules below are what reliably survives all three. When a rule here conflicts with normal web-design instincts, the rule wins.
Layout and styling:
- Structure with nested
<table role="presentation" cellpadding="0" cellspacing="0" border="0">— no flexbox, no grid, no floats, no position. One centered wrapper table, max-width 600px, single-column flow (stacked rows beat side-by-side columns). - Inline EVERY style on the element it styles. A
<style>block in<head>may additionally carry only what can't inline (media queries, dark-mode tweaks) — several clients drop it entirely, so the email must read correctly from inline styles alone. - No JavaScript anywhere (universally stripped). No external stylesheets. No web fonts — use email-safe stacks (Arial, Helvetica, Georgia, Verdana, Tahoma, 'Courier New') with generic fallbacks.
- Build the visual design out of colored table cells, borders, spacer cells, and type — not images. There is nowhere to host project images from here: a referenced project file will not exist for recipients. If imagery is essential, leave a clearly-marked placeholder cell with alt text and tell the user to swap in a hosted https URL before sending.
- Buttons are "bulletproof": a padded
<td>with bgcolor and inline border-radius, the<a>filling it with display:block and inline color — never an image, never a styled<button>.
Show full SKILL.md (127 more words)Show less
Client quirks that matter:
- Outlook (Word engine): give every table/cell explicit widths; set
line-height with mso-line-height-rule:exactly; wrap Outlook-only
fixes in
<!--[if mso]> … <![endif]-->conditionals. - Gmail clips messages beyond ~100KB of HTML — stay well under.
- Add
<meta name="color-scheme" content="light dark">and pick colors that survive dark-mode inversion (avoid pure#000/#fffbackgrounds; test text on mid-tone fills).
Deliverability and accessibility:
- First element in
<body>: a hidden preheader span (~85 chars) that previews next to the subject line. - alt text on any image, lang on
<html>, real<a href>links (no dead # anchors), and a footer with a plausible unsubscribe line and postal address for anything marketing-shaped.
Show the design at 600px; mention in your reply that the file is send-ready HTML the user can drop into their email tool.
© asgeirtj, CC0-1.0. 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 Anthropic/claude-design/skills/html-email of asgeirtj/system_prompts_leaks.
Open the folder on GitHubat commit 60d44cc
Compare with similar skills
HTML Email 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.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| HTML Email this skillasgeirtj/system_prompts_leaks | 69k | — | ~659 | Automated safety check: Pass | CC0-1.0 | |
| Web Artifacts Builderanthropics/skills | 180k | 40 repos | ~769 | Automated safety check: Pass | Apache-2.0 | |
| React Doctormakeplane/plane | 61k | 12 repos | ~657 | Automated safety check: Pass | AGPL-3.0 | |
| Impeccablebestofjs/bestofjs | 3.1k | 26 repos | ~2.6k | Automated safety check: Pass | MIT | |
| Figma Design System Builderwarpdotdev/warp | 65k | 2 repos | ~4.4k | Automated safety check: Pass | AGPL-3.0 | |
| Web Interface Guidelines Reviewervercel-labs/openreview | 1.7k | 97 repos | ~308 | Automated safety check: Pass | None |
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Categories
Questions about HTML Email
How do I install HTML Email in Claude Code?
Run `npx skills add asgeirtj/system_prompts_leaks --skill html-email -a claude-code`. Or copy the skill folder (Anthropic/claude-design/skills/html-email in asgeirtj/system_prompts_leaks) into .claude/skills/html-email in your project. Claude Code loads it when a task matches its description.
How do I install HTML Email in Codex?
Run `npx skills add asgeirtj/system_prompts_leaks --skill html-email -a codex`. Or copy the skill folder (Anthropic/claude-design/skills/html-email in asgeirtj/system_prompts_leaks) into .agents/skills/html-email in your project. Codex loads it when a task matches its description.
Can I use HTML Email 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 asgeirtj/system_prompts_leaks --skill html-email -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/html-email, .gemini/skills/html-email, .github/skills/html-email and .opencode/skills/html-email in your project.
What does HTML Email need to run?
SKILL.md names no scripts, command-line tools or credentials: HTML Email is instructions for the agent only.
Does HTML Email 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 HTML Email 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 HTML Email use?
HTML Email is published under the CC0-1.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does HTML Email use?
About 659 tokens (SKILL.md is roughly 2.6k 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 HTML Email?
Skills that share tags, products or a category with HTML Email: Web Artifacts Builder (anthropics/skills, 180k stars), React Doctor (makeplane/plane, 61k stars), Impeccable (bestofjs/bestofjs, 3.1k stars) and Figma Design System Builder (warpdotdev/warp, 65k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains HTML Email?
asgeirtj (a GitHub user) maintains it in asgeirtj/system_prompts_leaks, which has 69,280 GitHub stars. The repository holds 128 skills in this directory. The repository was last updated on October 10, 2026.
Source: asgeirtj/system_prompts_leaks on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.