HTML Entity Encoder / Decoder

HTMLエンティティのエンコード・デコード。
結果

Encode & Decode

Special characters or all characters (&#NNN;).

Two Modes

Special chars only or full numeric encoding.

Copy Result

One-click copy to clipboard.

Client-side

All processing in your browser. No data uploaded.

HTML Entity Encoder / Decoderについて

The HTML Entity Encoder/Decoder is an essential tool for web developers and content editors who need to safely embed special characters in HTML documents. HTML reserves certain characters — such as <, >, &, and " — for its own syntax, so using them raw in content can break page structure or create security vulnerabilities like Cross-Site Scripting (XSS). This tool converts those characters to their safe HTML entity equivalents (e.g., & becomes &) in encode mode, or reverses the process in decode mode. There is also a "Encode All" mode that converts every character to its numeric entity form (&#NNN;), which is useful for obfuscating email addresses or ensuring maximum compatibility across character sets. All processing happens entirely in your browser using the browser's own DOM — no data is ever sent to a server, keeping your content private.

HTML Entity Encoder / Decoderの使い方

  1. Select Encode or Decode mode using the toggle at the top of the tool.
  2. In Encode mode, choose between "Special chars only" (converts &, <, >, ", ') or "All characters" (converts every character to a numeric &#NNN; entity).
  3. Paste or type your text into the input textarea.
  4. The encoded or decoded result appears instantly in the output area below.
  5. Click the Copy button next to the result to copy the output to your clipboard.
  6. Paste the result into your HTML file, template engine, or CMS editor.

よくある質問

What is an HTML entity?

An HTML entity is a special text sequence that represents a character in HTML. It starts with & and ends with ;. For example, &amp;lt; displays as < without being interpreted as an HTML tag. Entities are used to display reserved characters and symbols that have special meaning in HTML.

Why do I need to encode HTML entities?

If you include raw < or > characters inside HTML content, the browser may interpret them as tag delimiters and break your page structure. Encoding them as &amp;lt; and &amp;gt; tells the browser to display the character visually rather than parse it as markup. This is also important for preventing XSS attacks in user-generated content.

What is the difference between "Special chars only" and "All characters" modes?

"Special chars only" encodes the five HTML-reserved characters: &, <, >, ", and '. "All characters" encodes every character as a numeric decimal entity like &#65; for the letter A. The latter is useful for obfuscation or ensuring compatibility with non-UTF-8 environments.

Is my data sent to a server?

No. All encoding and decoding is performed entirely in your browser. Your text never leaves your device. This makes the tool safe to use with sensitive or proprietary content.

Can I decode encoded email addresses?

Yes. If someone has encoded an email address using numeric entities to hide it from spam scrapers, you can paste it into the decoder to reveal the plain text version.

HTML Entity Encoder / Decoderの完全ガイド：無料オンラインツール

ブラウザ完結で安全・高速なHTML Entity Encoder / Decoder。開発者やクリエイターの作業を効率化

HTMLエンティティのエンコード・デコード。を瞬時に実現する無料ツールです。面倒なソフトのインストールは不要で、安全にブラウザ上で処理できます。

HTML Entity Encoder / Decoderが選ばれる理由

  • 高速処理: ミリ秒単位で即時実行。
  • プライバシー保護: データは端末外に送信されません。
  • 完全無料: 登録不要で制限なく利用可能。

簡単な3つの利用手順

  1. HTML Entity Encoder / Decoderのページを開きます。
  2. データを入力または貼り付けます。
  3. 結果を確認してコピーまたは保存します。

機能比較

項目 Metoolzy HTML Entity Encoder / Decoder 他社オンラインツール 専用ソフト
料金 完全無料 制限あり 有料ライセンス
セキュリティ 完全ローカル処理 サーバー送信あり ローカル処理

主な活用シーン

  • エンジニアの開発・デバッグ効率化
  • Web制作者の日常作業
  • データ変換・最適化

よくある質問 (FAQ)

入力したデータは保存されますか？

いいえ、すべてブラウザ内で処理され保存されません。