HTMLエスケープ
HTML特殊文字をエスケープまたはアンエスケープします。
HTMLエスケープ の使い方
- 1テキストまたはHTMLを貼り付ける
- 2エスケープでHTMLエンティティをエンコード、またはアンエスケープでデコード
- 3結果をコピーまたはダウンロード
HTMLエスケープ について
HTMLエスケープ/アンエスケープはHTMLで特別な意味を持つ文字（&、<、>、"、'）をHTMLエンティティに変換します。
HTMLエスケープの主な機能
- Escape the five core HTML special characters: &, <, >, ", '
- Unescape HTML entities back to their original characters
- Prevents XSS vulnerabilities when inserting text into HTML
- Handles named entities (&, <, >, ", ')
- One-click copy for escaped and unescaped output
- Works entirely in-browser — no data is sent to any server
- Instant conversion with real-time output
- Useful for rendering code examples and user-generated content safely
対応フォーマット
入力フォーマット
出力フォーマット
HTML5仕様に従って5つのコアHTML特殊文字をエスケープします。
使用例
Escape a code snippet for display in HTML
Make source code render as text rather than being parsed as HTML tags.
入力
<div class="box">Hello & World</div>
出力
<div class="box">Hello & World</div>
Unescape HTML entities from a database record
Convert stored HTML entities back to readable characters for editing.
入力
It's a "great" day & we're happy
出力
It's a "great" day & we're happy
主な使用ケース
- Safely inserting user-generated content into HTML templates to prevent XSS
- Displaying code examples in blog posts without them being parsed as HTML
- Preparing text for insertion into HTML email templates
- Decoding HTML entities stored in databases for editing
- Converting API response text containing entities to readable strings
- Escaping strings before inserting them into innerHTML calls
トラブルシューティング
Entities appear double-encoded like &amp;
解決策
The text was already escaped before you escaped it again. Unescape first to get the original characters.
Not all special characters are being escaped
解決策
This tool escapes the five core HTML characters. Extended entities like © or are not in scope.
Unescaping does not convert all entities
解決策
This tool handles the five core entities. Rare named entities like → may not be decoded — use a full HTML parser for comprehensive decoding.
よくある質問
Why escape HTML?
Unescaped characters like < and > are interpreted as HTML tags. Without escaping, user-submitted text containing <script> tags can execute arbitrary JavaScript — a cross-site scripting (XSS) attack.
Which characters are escaped?
The five core HTML special characters: & → &, < → <, > → >, " → ", ' → '.
What is the difference between HTML escaping and URL encoding?
HTML escaping converts characters to HTML entities for safe rendering inside HTML. URL encoding converts characters to %XX hex format for safe use in URLs.
Should I escape or sanitize user content?
For displaying user content as plain text in HTML, escaping is sufficient. If you need to allow some HTML tags, use a trusted HTML sanitizer library.
Is HTML escaping enough to prevent XSS?
Escaping is the primary defense when inserting text into HTML content. However, the correct escaping strategy depends on context — JS strings, HTML attributes, and URLs each require different rules.
What does &amp; mean?
&amp; is a double-encoded ampersand — it renders as & in the browser. This usually occurs when content is escaped twice.
Is my data sent to a server?
No. All escaping and unescaping is performed in your browser using JavaScript string replacement.
Can I use this to prepare content for JSON inside HTML?
For JSON in HTML (e.g., inside a <script> tag), use JSON.stringify and ensure the string is placed correctly. HTML entity escaping alone is not sufficient.