HTMLフォーマッター
トレンド 🔥HTMLコードをフォーマット・整形
HTMLフォーマッター の使い方
- 1入力エリアに HTML コードを貼り付ける
- 2フォーマットまたは最小化を選択
- 3処理済み HTML を確認
HTMLフォーマッター について
HTML フォーマッターは HTML コードをフォーマット、最小化、検証するツールです。インデントを正しく整理し、コードの可読性を向上させます。
HTMLフォーマッターの主な機能
- Beautify and indent HTML code with consistent formatting
- Minify HTML to remove whitespace for production use
- Handles nested elements, attributes, and inline content
- Preserves content inside <pre>, <script>, and <style> tags
- Works with HTML fragments and complete HTML documents
- Works entirely in-browser — no server uploads
- One-click copy of formatted or minified output
- Configurable indentation (2-space or 4-space)
使用例
Beautify minified HTML from a template engine
Format a single-line HTML string from a server-side template for code review.
入力
<html><head><title>Page</title></head><body><h1>Hello</h1><p>World</p></body></html>
出力
<html>
<head>
<title>Page</title>
</head>
<body>
<h1>Hello</h1>
<p>World</p>
</body>
</html>Minify HTML for a landing page deployment
Remove all whitespace from a formatted HTML file before deploying to a CDN.
入力
Well-indented HTML page, ~150 lines
出力
Single-line minified HTML — ~30% smaller file size
主な使用ケース
- Formatting HTML from CMS templates or server-rendered pages for debugging
- Reviewing HTML structure in code reviews by making nesting levels visible
- Minifying HTML for production deployments to reduce page load size
- Cleaning up HTML copied from a browser DevTools inspector
- Formatting HTML snippets from third-party widgets or embed codes
- Preparing HTML for documentation or technical writing by making it readable
トラブルシューティング
Inline elements like <span> get placed on separate lines
解決策
HTML formatters typically place each element on its own line for clarity. This is expected formatting behavior — in production, the minifier will collapse whitespace back for display purposes.
Content inside <script> or <style> tags is mangled
解決策
Ensure your HTML formatter recognizes <script> and <style> as raw text elements. Well-implemented formatters preserve their inner content exactly. If content is changed, try formatting the JavaScript/CSS separately.
Self-closing tags like <br> cause formatting errors
解決策
HTML5 uses void elements (not self-closed), while XHTML uses <br/>. The formatter uses the browser's DOMParser which normalizes to HTML5 conventions. Ensure your HTML is valid HTML5.
よくある質問
Does it validate HTML?
Basic formatting uses the browser DOMParser which will flag some structural issues. Full W3C validation (checking against the HTML5 spec in detail) is not included. Use the W3C HTML Validator for compliance checking.
Can I format just a fragment of HTML?
Yes. The formatter handles both complete HTML documents and standalone fragments like a <div> with nested children. You do not need to include <html>, <head>, or <body> tags.
Does it support HTML5 custom elements?
Yes. The browser's DOMParser accepts custom elements (like <my-component>) and treats them as valid unknown elements. They are formatted with the same indentation rules as standard elements.
Can I minify HTML to reduce page size?
Yes. The minify mode removes all unnecessary whitespace (indentation, extra newlines) from HTML while preserving content. Combined with server-side Gzip compression, this can noticeably reduce the transferred HTML size.
Does minifying HTML affect SEO?
No. Search engine crawlers parse the HTML DOM, not the raw text. Whitespace-only changes have no effect on how search engines read your content or structure.
What indentation style is used?
The formatter uses 2-space indentation by default. Some configurations support 4-space indentation. Consistent indentation is applied to every nesting level.
Is my code sent to a server?
No. All formatting is performed locally in your browser using the DOMParser API. Your HTML code never leaves your device.
Will it break my HTML if I format then minify?
No. Both operations only affect whitespace. The actual elements, attributes, and content are identical before and after formatting or minification. You can round-trip between the two without data loss.