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Agent skill

Doctype

by thedaviddias in thedaviddias/Front-End-Checklist

A skill your agent uses when applies to all HTML documents. An agent skill from thedaviddias/Front-End-Checklist.

MITAuto-check passedFrontend & Design

Install Doctype

skills CLI
$ npx skills add thedaviddias/Front-End-Checklist --skill doctype -a claude-code

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

GitHub CLI
$ gh skill install thedaviddias/Front-End-Checklist doctype --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/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/doctype .claude/skills/doctype && 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
doctype
GitHub stars
74k
Token cost
~831 tokens
SKILL.md length
401 words
Files
2 (incl. references)
Skills in repo
390
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when applies to all HTML documents. An agent skill from thedaviddias/Front-End-Checklist.

  • Applies to all HTML documents
  • SKILL.md covers Quick Reference, Check, Fix and Explain, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
  • Tasks that involve Backend development

What it does

Doctype is an agent skill from thedaviddias/Front-End-Checklist. Use when applies to all HTML documents. Always check the very first line of the raw HTML source (view-source: or DevTools Network Response). In SSR frameworks, check the root HTML template (e.g., document.tsx in Next.js, index.html in Vite/Vue, application.html.erb in Rails). The doctype is not a tag — it is a declaration and does not need a closing tag.

Its SKILL.md is about 830 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/rule.md`).

It sits in Frontend & Design, covering Backend development and React components. It works with Next.js, Vite and Vue.js. The repository describes itself as: 🗂 The essential checklist for modern web development, for humans and AI agents. The licence is MIT.

When your agent uses it

  • Applies to all HTML documents
  • Tasks that involve Backend development
  • Tasks that involve React components

Example prompts

  • “/doctype”

What it can do on your machine

Read from SKILL.md and the folder at commit e8d14d0. 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

    Links to these hosts (documentation or services it may open):

    • frontendchecklist.io

    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

Doctype loads about 831 tokens when it runs, and up to ~1.6k if it reads all its reference files. Until then it costs about 92 tokens; SKILL.md has 401 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~92
When it runs · the whole SKILL.md, loaded when a task matches
~831
With references · SKILL.md plus every file in references/, read only if the agent opens them
~1.6k

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 thedaviddias/Front-End-Checklist at commit e8d14d0, republished under its MIT licence (© thedaviddias). 401 words, ~831 tokens.

Download SKILL.mdSave it as .claude/skills/doctype/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
doctype
description
Use when applies to all HTML documents. Always check the very first line of the raw HTML source (view-source: or DevTools > Network > Response). In SSR frameworks, check the root HTML template (e.g., _document.tsx in Next.js, index.html in Vite/Vue, application.html.erb in Rails). The doctype is not a tag — it is a declaration and does not need a closing tag.
metadata.category
html
metadata.priority
critical
metadata.difficulty
beginner
metadata.estimatedTime
5
metadata.source
frontendchecklist.io
metadata.url
https://frontendchecklist.io/rules/html/doctype

Use the HTML5 doctype

Without the HTML5 doctype, browsers fall back to Quirks Mode, which emulates the rendering behavior of pre-standards browsers from the late 1990s. In Quirks Mode, the CSS box model changes (padding adds to element width), vertical centering breaks, and many modern HTML5 APIs may behave unexpectedly. This causes cross-browser rendering inconsistencies that are difficult to debug and may produce inaccessible layouts.

Quick Reference

  • Every HTML document must begin with <!DOCTYPE html> as its very first line
  • Without a doctype, browsers enter Quirks Mode — a legacy compatibility mode with inconsistent CSS and JavaScript behavior
  • The HTML5 doctype is case-insensitive but <!DOCTYPE html> (uppercase DOCTYPE) is the conventional form
  • No other content, not even whitespace or BOM characters, should appear before the doctype
  • Frameworks like Next.js, Nuxt, and Remix automatically include the doctype — verify in rendered HTML, not source templates

Check

Check the very first line of the HTML document source (not the DOM — the raw HTTP response). The document must begin with <!DOCTYPE html> (case-insensitive). Flag if: (1) the doctype is missing entirely; (2) an old HTML4 or XHTML doctype is used (contains PUBLIC and a DTD URL); (3) the doctype is not the absolute first content (whitespace or BOM before it triggers some browsers to enter Quirks Mode); (4) the doctype has incorrect syntax.

Show full SKILL.md (183 more words)Show less

Fix

Add <!DOCTYPE html> as the absolute first line of the HTML document, before the <html> tag. Remove any old HTML4 or XHTML doctypes. Ensure no whitespace, comments, or BOM markers precede the doctype. For framework projects: verify in the root HTML template file, and confirm in the rendered HTML by viewing page source in the browser.

Explain

The DOCTYPE declaration tells the browser which version of HTML the document uses. <!DOCTYPE html> activates Standards Mode (also called Full Standards Mode) in all modern browsers, ensuring consistent rendering behavior. Without it, browsers enter Quirks Mode to emulate old IE behavior — a compatibility mode that changes the box model, float clearing, table rendering, and other CSS behaviors. The HTML5 doctype was intentionally made simple (just <!DOCTYPE html>) to replace the verbose HTML4/XHTML doctypes that required a full DTD URL.

Code Review

Review templates, server-rendered HTML, and shared components that output markup related to Use the HTML5 doctype. Flag exact elements, attributes, and routes where the rendered HTML violates the rule.

For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/rules/html/doctype

© thedaviddias, 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 1 other file (references) in skills/doctype of thedaviddias/Front-End-Checklist.

  • SKILL.md
  • references/rule.md

Open the folder on GitHubat commit e8d14d0

Compare with similar skills

Doctype 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.

Doctype compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Doctype this skillthedaviddias/Front-End-Checklist74k—~831Automated safety check: PassMIT
Vue Component Developmentgdarko/laravel-vue-starter145—~1.1kAutomated safety check: PassMIT
Tanstack Startasmyshlyaev177/test-proxy-recorder78—~2.9kAutomated safety check: NotesMIT
React Best Practicesryokun6/ryos1.3k—~2kAutomated safety check: PassMIT
Chakra UI v3 Builderchakra-ui/chakra-ui41k—~3.1kAutomated safety check: PassMIT
Creative Tim UI Blockscreativetimofficial/ui12k—~2.1kAutomated safety check: NotesMIT

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Works with

Categories

Questions about Doctype

What does Doctype do?

A skill your agent uses when applies to all HTML documents. An agent skill from thedaviddias/Front-End-Checklist. Doctype is an agent skill from thedaviddias/Front-End-Checklist. Use when applies to all HTML documents.

When should I use Doctype?

Doctype fits situations like: applies to all HTML documents; tasks that involve Backend development; tasks that involve React components.

How do I install Doctype in Claude Code?

Run `npx skills add thedaviddias/Front-End-Checklist --skill doctype -a claude-code`. Or copy the skill folder (skills/doctype in thedaviddias/Front-End-Checklist) into .claude/skills/doctype in your project. Claude Code loads it when a task matches its description.

How do I install Doctype in Codex?

Run `npx skills add thedaviddias/Front-End-Checklist --skill doctype -a codex`. Or copy the skill folder (skills/doctype in thedaviddias/Front-End-Checklist) into .agents/skills/doctype in your project. Codex loads it when a task matches its description.

Can I use Doctype 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 thedaviddias/Front-End-Checklist --skill doctype -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/doctype, .gemini/skills/doctype, .github/skills/doctype and .opencode/skills/doctype in your project.

What does Doctype need to run?

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

Does Doctype access the network?

SKILL.md names 1 domain. As links in the text: frontendchecklist.io. This is read from the text; nothing was executed.

Is Doctype 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 Doctype use?

Doctype 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 Doctype use?

About 831 tokens (SKILL.md is roughly 3.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 801 tokens, read only when the agent opens those files.

What are the alternatives to Doctype?

Skills that share tags, products or a category with Doctype: Vue Component Development (gdarko/laravel-vue-starter, 145 stars), Tanstack Start (asmyshlyaev177/test-proxy-recorder, 78 stars), React Best Practices (ryokun6/ryos, 1.3k stars) and Chakra UI v3 Builder (chakra-ui/chakra-ui, 41k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Doctype?

thedaviddias (a GitHub user) maintains it in thedaviddias/Front-End-Checklist, which has 74,421 GitHub stars. The repository holds 390 skills in this directory. The repository was last updated on October 6, 2026.

Source: thedaviddias/Front-End-Checklist on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.