Base64 Encoder / Decoder

How to Use the Base64 Encoder / Decoder

This free online Base64 tool lets you encode any text to Base64 format or decode Base64 strings back to readable text. Simply paste your input, choose your mode, and click the button. Everything runs in your browser with no server communication.

What is Base64?

Base64 is a binary-to-text encoding scheme that represents binary data as a string of printable ASCII characters. It is commonly used to embed images in HTML or CSS, transmit binary data in JSON or XML, encode email attachments (MIME), and store complex data in URLs or cookies.

When to Use Base64

Base64 encoding is useful when you need to transmit binary data through text-based protocols. Common use cases include embedding small images directly in HTML, sending binary attachments via email, and encoding authentication tokens. Note that Base64 increases data size by approximately 33%, so it should not be used for large files.

UTF-8 Support

This tool fully supports UTF-8 characters including accented letters, Asian characters, and emoji. The encoding process first converts the text to UTF-8 bytes, then encodes those bytes to Base64, ensuring accurate round-trip conversion.

Base64エンコード・デコードツールについて

このツールはテキストをBase64形式にエンコードしたり、Base64文字列を元のテキストにデコードできます。UTF-8に完全対応しており、全ての処理はブラウザ内で完結するためデータがサーバーに送信されることはありません。メール添付やHTML埋め込み画像、認証トークンの確認などに便利です。