2026-04-22 · 読了目安 1 分
Base64 と URL エンコードの使い分け
Base64はバイト表現、URLエンコードはURI予約文字の安全化に使います。
Use Base64 when you must represent binary or opaque bytes in text channels.
Use URL encoding when text is placed into query strings or path segments where reserved characters matter.
この比較の見方
These techniques solve different layers. Base64 transforms bytes to text; URL encoding escapes reserved URI characters.
| アプローチ | データ処理 | 一般的な速度 | 適した用途 |
|---|---|---|---|
| Base64 encode/decode | Converts bytes to ASCII-like text; output often includes +, /, = | Fast for small payloads; size grows by about one third | JWT segments, binary blobs in text protocols, quick clipboard-safe transport |
| URL encode/decode | Escapes reserved URI characters (%xx) for safe transport in URLs | Fast; output length depends on special-character density | Query parameters, callback URLs, redirect targets, form-encoded values |
要点
- If the destination is a URL field, prefer URL encoding even when source content is plain text.
- If the destination expects a byte-preserving textual envelope, use Base64 and document charset assumptions.